Unit 2: Atomic Theory Unit Notes & CW

Transcription

1 Name: Perid: Unit 2: Atmic Thery Unit Ntes & CW Unit Objectives: Understand that the mdern mdel f the atm has evlved ver a lng perid f time thrugh the wrk f many scientists Discuss the evlutin f the atmic mdel Relate experimental evidence t mdels f the atm Identify the subatmic particles f an atm (electrn, prtn, and neutrn) Knw the prperties (mass, lcatin, and charge) f subatmic particles Determine the number f prtns, electrns, and neutrns in a neutral atm and an in Calculate the mass number and average atmic weight f an atm Differentiate between an anin and a catin Give brief descriptin f Gld Fil experiment and state cnclusins Distinguish between grund and excited state electrn cnfiguratins Identify and define istpes Write electrn cnfiguratins Generate Bhr diagrams Differentiate between kernel and valence electrns Draw Lewis Dt Diagrams fr an element r an in Fcus Questins fr the Unit: What is the structure f an atm? Hw did the mdel f the atm change ver time? Hw des the structure f an atm relate t chemical prperties f elements? YOU SHOULD BE ABLE TO ANSWER THESE IN DETAIL BY THE END OF THE UNIT Define the fllwing vcabulary: Alltrpe Atm Atmic Mass unit (a.m.u.) Bhr mdel Cmpund Electrn Cnfiguratin Excited state In Lewis Dt Diagram Neutrn Anin Atmic Mass Atmic number Catin Electrn Element Grund state Istpe Mass number Nuclear Charge 1

2 The bld, underlined wrds are imprtant vcabulary wrds that yu shuld be able t define and use prperly in explanatins. This is a study guide fr what yu will be tested n thrughut the year. The bjectives are divided int categries f Knwledge (what yu have t knw) and Applicatin (what yu have t be able t d) ) ATOMIC CONCEPTS Knwledge Applicatin Explain what happened during the gld-fil experiment and what it Atms are the basic unit (building shwed. blck) f matter. Gld fil was bmbarded (hit) with Atms f the same kind are called psitively charged alpha particles. Mst elements. alpha particles passed thrugh the gld fil, The mdern mdel f the atm has but sme were deflected. This shwed that: develped ver a lng perid f time 1. the atm is mstly empty space thrugh the wrk f many scientists. 2. the nucleus is small, psitively charged, and lcated in the center f the atm The three subatmic particles that make up an atm are prtns, neutrns, and electrns. The prtn is psitively charged, the neutrn has n charge, and the electrn is negatively charged. (This is als referenced n Table O. Check it ut!) Each atm has a nucleus with an verall psitive charge, made up f Determine the nuclear charge f an prtns and neutrns. atm. (equal t the number f The nucleus is surrunded by negatively prtns in the nucleus) charged electrns. Atms are electrically neutral, which means that they have n charge (# prtns = # electrns) Ins are atms that have either lst r gained electrns and are either psitively r negatively charged When an atm gains ne r mre electrns, it becmes a negative in and its radius increases. When an atm lses ne r mre electrns, it becmes a psitive in and its radius decreases. The mass f each prtn and each neutrn is apprximately equal t ne atmic mass unit (AMU). An electrn is much less massive (has almst n mass) cmpared t a prtn r neutrn. Determine the number f prtns r electrns in an atm r in when given ne f these values. (Peridic Table) Cmpare the atmic radius and inic radius f any given element Ex: A chlride in has a larger radius than a chlrine atm because the in has an extra electrn. A sdium in has a smaller radius than a sdium atm because the in has lst an electrn. Calculate the mass f an atm given the number f prtns and neutrns Calculate the number f neutrns r prtns, given the ther value 2

3 In the mdern mdel f the atm, the WAVE-MECHANICAL MODEL (electrn clud), the electrns are in rbitals (cluds), which are defined as regins f mst prbable electrn lcatin. Each electrn in an atm has a specific amunt f energy. Electrns clsest t the nucleus have the lwest energy. As an electrn mves away frm the nucleus, it has higher energy. Electrn cnfiguratins shw hw many electrns are in each rbital. When all f an atm s electrns are in the rbitals clsest t the nucleus, the electrns are in their lwest pssible energy states. This is called the grund state. When an electrn in an atm gains a specific amunt f energy, the electrn is at a higher energy state (excited state) When an electrn returns frm a higher energy (excited) state t a lwer energy (grund) state, a specific amunt f energy is emitted. This emitted energy can be used t identify an element. The flame test is an example f the bright-line spectrum visible t the naked eye. The clr can determine the identity f a psitive in in a cmpund. The utermst electrns in an atm are called the valence electrns. In general, the number f valence electrns affects the chemical prperties f an element. Atms f an element that cntain the same number f prtns but a different number f neutrns are called istpes f that element. The average atmic mass f an element is the weighted average f the masses f its naturally ccurring istpes. Distinguish between grund state and excited state electrn cnfiguratins. (Be careful t keep the same number f electrns when writing the excited state.) Identify an element by cmparing its bright-line spectrum t given spectra Draw a Lewis electrn-dt structure f an atm. Distinguish between valence and nn-valence electrns, given an electrn cnfiguratin Calculate the number f neutrns in an istpe f an element given the istpe s mass Given an atmic mass, determine the mst abundant istpe Calculate the atmic mass f an element, given the masses and abundance f naturally ccurring istpes Gal setting: Based upn yur learning style results and the infrmatin abve list at least tw techniques yu plan t use t study during this unit What grade wuld yu like t achieve n this unit based n yur effrts? % 3

4 Lessn 1: Cncept f an Atm Objective: T cmpare and cntrast the develpment f the mdels f the atm. Often in science, we are nly aware f a certain amunt f infrmatin at a time. As we learn new facts, we can edit ur current knwledge and develp deeper understandings f what we are studying. This is why science is ften changing... we are cnstantly learning new things! We learned in Unit 1B that the smallest unit f matter is called an element. The cncept f an atm Atmic mdels are theries that describe what the physical prperties f an atm are (hw it lks structurally). These physical prperties will help determine the chemical prper ties f an atm (hw it behaves). Our current mdel f the atm, the electrn clud mdel, is based n all the nes that came befre it. 4

5 Please watch the fllwing vide: Structure f an Atm The Atm Backgrund & Histry Atm: It is the basic building blck f matter; 1. Demcritus = (450 BC) Greek man wh tried t answer the questin abut the divisibility f matter; 2. Daltn (1803) Knwn as the funder f the atmic thery Daltn invented the wrd atm as the basic unit f matter which were He als discvered that atms f different elements have different prperties and masses Fund that cmbining atms f different elements frmed cmpunds Thery referred t as the cannnball thery because it lked like a simple sphere with unifrm density. 3. J.J. Thmsn (1897) View the fllwing link : Cathde ray tube Yu can find this n my website! While using a cathde ray tube he discvered that the ray was deflected (due t a magnetic/electrical field) 5

6 4. Ernst Rutherfrd (1909) Simulatin: Tw cnclusins were therefre made: 1) 2) 5. Neils Bhr (1913) 6. Wave-Mechanical/Clud Mdel (Mdern, present-day mdel) Develped after the famus discvery that energy is made up f bth waves and particles Still the same dense psitively nucleus Many scientist have cntributed t this thery 6

7 LAB: Ernest Rutherfrd s 1911 Gld Fil Experiment (Simulatin) PURPOSE: The purpse f this activity is t simulate Rutherfrd s famus Gld Fil Experiment t demnstrate hw infrmatin can be gained abut smething that cannt be seen r directly measured. MATERIALS: 7 marbles 1 meter stick masking tape 2 rulers PROCEDURE: 1. Divide int 3 students per grup. 2. Use masking tape t make a line (in the hallway r in the classrm) n the flr that is 60 cm lng. 3. Make marks n the tape at the 5cm, 15cm, 25cm, 35cm, 45cm, and 55cm. 4. Place ne marble n each mark. 5. Measure 1 meter perpendicularly frm the center f the tape (with marks ). Mark this spt with a small piece f tape. 6. Place the seventh marble n this spt. 60 cm tape 1 meter Target marbles n 60 cm tape alpha marble n tape spt 7. One team member, while sitting n the flr, facing away frm tape and target marbles will rll the alpha marble (the marble representing the alpha particle) tward the center f the tape. This will be repeated fr 50 trials fr each team member. Yu try t be as cnsistent (minimum variatins) as pssible. 8. A secnd team member will recrd whether r nt each trial is a hit r a miss A trial will cunt as a hit r miss nly if the alpha marble passes ver the 60 cm tape. If the target marble is mved, even slightly, the trial is registered as a hit. If the target is nt mved the trial is a miss. 9. The third team member replaces the target marbles and returns the alpha marble t the team member rlling at the time. 10. Team members switch psitins after each 50 trials. 11. Recrd all 150 trials. 12. Measure the diameter f ne f the target marbles n the 60 cm tape. Place all 7 marbles next t the calibrated edge f the meter stick. Divide the measurement f the 7 marbles by seven t btain the average diameter f the target marble. 13. Cmplete recrding all data cllectin and calculatins. 14. Prepare fr Rutherfrd Lab Quiz using similar, but nt identical SAMPLE DATA. 7

8 NAME: BOCK: DATE: CALCULATIONS 1. Calculate the diameter f the spheres using the fllwing frmula: field width X number f hits Diameter = 2 X number f target marbles X number f trials Field width = Tt. Hits = # Target Marbles = # Trials = Calculatins 2. Calculate the percent errr using the fllwing equatin: measured value calculated value % Errr = X 100 measured value Measured value = Calculated value = CALCULATIONS: Calculated diameter value DISCUSSION What wuld happen if the target marbles were smaller r larger? Assuming yur prcedure is cnsistent, wuld a greater number f trials increase yur precisin? 1. On what des the hit/miss rati depend? 2. Hw des the number f trials affect the results? % Errr = 3. Wuld ne millin trials cause the calculated diameter t be significantly clser t the measured value than the 150 trials? In ther wrds, if Rutherfrd s experiment were repeated tday, a thusand times wuld the results be different? Explain. 8 Data Stu 1 Stu 2 Stu3 # Hit # Hit # Hit Tt Tt Tt Grand Ttal Hits

9 Classwrk 2-1: Cncept f an Atm Objective: T cmpare and cntrast the develpment f the mdels f the atm. 1. Draw belw the mdel f the atm prpsed be the fllwing individuals Daltn (1800) Thmpsn (1897) Bhr (1913) 2. Hw did Thmpsn s mdel differ frm Daltn s mdel? 3. The gld fil experiment resulted in tw majr discveries which were made abut the structure f the atm. What were they? a. b. 4. Hw des the Bhr mdel represent electrns arund the central nucleus? Why (think f spectra)? 9

10 Practice: 10

11 6) Explain the current mdel f the atm. 11

12 Lessn 2: Subatmic Particles Objective: T define the parts f an atm Please watch the fllwing vide: Bill Nye Atms Each subatmic particle has very unique physical prperties that will in turn; affect the chemical prperties f the atms they make up. The fllwing reading passage will help yu t better understand the structure f the atm. Understanding Atmic Structure... The wrd nucleus f the atm is just like the nucleus f the cell that yu learned abut in Living Envirnment. One f the prperties f the nucleus is that it is very dense cmpared t the rest f the atm. This is a qualitative bservatin. T put this int quantitative terms, we say that each f the subatmic particles fund in the nucleus has an apprximate relative mass f 1 amu r atmic mass unit. The majrity f the atm s mass cmes frm the dense center f the atm (the nucleus). Hwever, mst f the atm is nt dense; it is made f empty space. Have yu ever heard f the idea that ppsites attract? This principle cmes frm science. Psitives and negatives attract ne anther and this attractin hlds the atm tgether. Psitively charged particles The negatively The third type Each f the three types f subatmic particles has a different charge s that they can all c-exist in the small space that is the atm. - Each type f atm has a specific number f prtns. - The wrd atm implies that the We can use the reference table t help us with many f these symbls and definitins. Lk at the key n the peridic table. 12

13 Symbl and Name-: In cmpunds ntatin the symbls are used. When just referring t the element itself it can be written tw ways: C-12 (symbl and mass number) r 12 (mass number) C 6 (atmic number) Atmic Number- Atmic Mass- Electrns- Fr a neutral atm, Nuclear Charge = p = nuclear charge Nuclens = 13

14 Subatmic Particle Prtn Charge Relative Mass Lcatin Symbl Hw t Calculate Neutrn Electrn 14

15 Classwrk 2-2: Subatmic Particles & Their Prperties Objective: T define the parts f an atm 1. Fill in the blanks The mdern mdel f the atm has evlved ver a lng perid f time thrugh the wrk f many scientists. Each atm has a nucleus, with an verall psitive charge, surrunded by ne r mre negatively charged. Subatmic particles cntained in the nucleus include and. The prtn is psitively charged, and the neutrn has n charge. The electrn is charged. Prtns and electrns have equal but ppsite charges. The number f prtns the number f electrns in an atm. The mass f each prtn and each neutrn is apprximately atmic mass unit. An electrn is much massive than a prtn r a neutrn. The number f prtns in an atm ( ) identifies the element. 2. Fill in the fllwing table: Particle Charge Mass Lcatin neutrn +1 1 electrn 15

16 Practice: 1.) In the mdern mdel f the atm, each atm is cmpsed f three majr subatmic particles. a) Name the subatmic particles cntained in the nucleus f the atm. b) State the charge assciated with each type f subatmic particle cntained in the nucleus f the atm. c) What is the net charge f the nucleus? 2.) Give the names and chemical symbls fr the elements that crrespnd t these atmic numbers: a. 10 b. 18 c. 36 d ) What is the charge n the nucleus f a) a Cr atm? b) a Ni atm? c) a sdium atm? 4.) Which statement best describes electrns? (1) They are psitive subatmic particles and are fund in the nucleus. (2) They are psitive subatmic particles and are fund surrunding the nucleus. (3) They are negative subatmic particles and are fund in the nucleus. (4) They are negative subatmic particles and are fund surrunding the nucleus. 5.) The atmic number f an atm is always equal t the number f its (1) prtns, nly (2) neutrns, nly (3) prtns plus neutrns (4) prtns plus electrns 6.) Which particles are fund in the nucleus f an atm? (1) electrns, nly (3) neutrns, nly (2) prtns and electrns (4) prtns and neutrns 16

17 7.) A neutral atm cntains 12 neutrns and 11 electrns. The number f prtns in this atm is (1) 1 (2) 11 (3) 12 (4) 23 8.) Which statement is true abut the charges assigned t an electrn and a prtn? (1) Bth an electrn and a prtn are psitive. (2) An electrn is negative and a prtn is psitive. (3) An electrn is psitive and a prtn is negative. (4) Bth an electrn and a prtn are negative. 9.) What is the charge f the nucleus in an atm f xygen-17? (1) 0 (2) -2 (3) +8 (4) Using the definitins prvided abve please fill in the fllwing chart. Symbl # Prtns # Neutrns # Electrns Atmic Number Mass Number Nuclear Symbl 35 Cl C

18 Lessn 3: Subatmic Particles & Ins Objective: T cmpare and cntrast the subatmic particles f atms and ins. Atms Neutral atms A neutral sdium atm, fr example, cntains 11 prtns and 11 electrns. By remving an electrn frm this atm we get a psitively charged Na + in that has a net charge f +1. Atms that gain A neutral chlrine atm, fr example, cntains 17 prtns and 17 electrns. By adding ne mre electrn we get a negatively charged Cl - in with a net charge f -1. The gain r lss f electrns by an atm t frm negative r psitive ins has an enrmus impact n the chemical and physical prperties f the atm. Sdium metal, fr example, which cnsists f neutral sdium atms, bursts int flame when it cmes in cntact with water. Neutral chlrine atms instantly cmbine t frm Cl 2 mlecules, which are s reactive that entire cmmunities are evacuated when trains carrying chlrine gas derail. Psitively charged Na + and negatively charged Cl - ins are s unreactive that we can safely take them int ur bdies whenever we salt ur fd. Catins are 18

19 Classwrk 2-3: Subatmic Particles & Ins Objective: T cmpare and cntrast the subatmic particles f atms and ins. 1.) In terms f subatmic particles, what is the difference between an atm and an in? 2.) Hw can yu determine the electrical charge n an in? 3.) When an atm becmes an in, des the element s nucleus change? 19

20 Practice: Fr the fllwing atms/ins determine the number f prtns, neutrns, electrns, mass number, and nuclear charge. ATOM r ION? PROTONS NEUTRONS ELECTRONS MASS NUMBER NUCLEAR CHARGE 15 N Cu +2 8 B O F Pb 208 Pb Ag +1 Zn +2 Mg S -2 Challenge: Directins: Answer the fllwing questins n a separate sheet f paper fr extra credit. Yu must answer ALL questins fr credit! 1.) Irn lses 3 electrns t frm an in, what is the electrical charge f the in? 2.) Oxygen gains 2 electrns t frm an in, what is the electrical charge f the in? 3.) What number is the Lwest Cmmn Multiple f the numbers 3 and 2? 4.) Irn reacts with xygen in the air t frm the electrically neutral cmpund, irn (III) xide, knwn as rust. Hw many f each type f in wuld be needed t frm an electrically neutral cmpund? 5.) Write the chemical frmula fr irn (III) xide. 20

21 Lessn 4 Subatmic Particles & Istpes Objective: T differentiate between istpic frms f atms based n number f neutrns Atms are identified by the numbers f prtns, neutrns, and electrns that they cntain. Befre yu can understand the prperties f atms, hw atms cmbine t frm mlecules, and the prperties f mlecules, yu must be familiar with the number f prtns, neutrns, and electrns assciated with atms. Frm the perspective f a chemist, the entire wrld is cmpsed f atms, and atms are cmpsed f prtns, neutrns, and electrns. Prtns and neutrns are abut 2000 times heavier than an electrn. A prtn has a charge f +1, a neutrn has n charge, and an electrn has a charge f -1. The nucleus is very dense and very small cmpared t the entire atm. If I take a sample f air frm this rm and put it int a bx, there may be mre than ne type f hydrgen atm. Remember that in rder fr an atm t be hydrgen, it must have a certain number f prtns (prtns determine the identity f an element). The prperties f atms are determined by the numbers f prtns, neutrns, and electrns that they cntain. Atms with the same number f prtns but different number f neutrns are called istpes f an element. In Earth Science, yu learned abut Isbars. Isbars are lines (like the nes shwn belw) that represent areas f the same pressure. Is- is a prefix that means same -tpe sunds like type... The istpic ntatin fr an atm includes the fllwing infrmatin: symbl f the element, the element s atmic number (Z) which specifies the number f prtns in the nucleus, and the mass number (A) which indicates the number f prtns plus neutrns in the nucleus. [The number f electrns in a neutral atm is equal t the number f prtns in the nucleus f the atm. The mass cntributed by the electrns in an atm is very small, s it is nt included when calculating the mass number.] Atmic Symbl Ntatin 21

22 ISOTOPES AND MASS Istpe = Example: Istpes f Carbn (C-12, C-13, & C-14) C C C S why des Carbn have a mass f n the Reference Table? (there exist three different istpes f carbn in the atmsphere as seen just abve) Atmic Mass = the weighted average f an element s naturally ccurring istpes 22

23 23.99 X.7899 = X.1000 = X.1101 = 23

24 Practice: 1. Use a peridic table t fill in the missing infrmatin in the fllwing table. Which elements listed in the table are istpes? 2. A mystery element ccurs in nature as tw istpes. Istpe A has a mass f amu and its abundance is 19.9%; Istpe B has a mass f amu and its abundance is 80.1%. Frm this data, calculate the atmic mass f the element and shw all wrk. Lastly, identify the element using yur Peridic Table. 24

25 Classwrk 2-4: Subatmic Particles & Istpes Objective: T differentiate between istpic frms f atms based n number f neutrns 1. What infrmatin is prvided by the atmic number? 2. What infrmatin is prvided by the mass number? 3. Calculate the atmic mass f cpper using the data belw. SHOW ALL WORK. Element Mass Percent Abundance cpper amu 69.17% cpper amu 30.83% Describe the similarities between 17Cl and 17 Cl Describe the differences between 17Cl and 17 Cl. 25

26 Activity - Sweet Mdel f the Atm Purpse The purpse f this lab is t visually see hw atms, istpes and ins are put tgether. Materials D nt eat any f yur materials until yu are instructed t d s. M&M s Skittles Nerds Prcedure 1. Establish which subatmic particle each type f candy represents. Electrns: Prtns: Neutrns: 2. Yu need a piece f lse leaf paper t carry ut the lab. 3. Fr the fllwing examples, be sure t make them using yur candies. When yu have made the mdel with yur candy, draw the atm n yur paper. 4. Be sure t answer the questins as yu cmplete the activity. ATOMS Si Ne e- e - p + p + n n Which f the tw atms abve d yu think is happiest (in scientific terms that means mre stable)? Why? (Hint: think abut which element has a Stable Octet r FULL valence shell d yu think this is a gd situatin fr an atm?) ISOTOPES The mst cmmn istpe f S is A less cmmn istpe f S culd be e- e - p + p + n n Explain hw yu determined the mst cmmn istpe. 26

27 IONS A psitive in (catin) is made by. A negative in (anin) is made by. Make the fllwing atm and its mst stable in P P (fill in the charge) e- e - p + p + n n Al Al (fill in the charge) e- e - p + p + n n Hw many electrns prefer t be in the uter mst shell? This is called the ctet rule. Analysis Fr these ins, yu d nt have t make the atms with yur candies unless yu get stumped. Answer the fllwing questins: 1. Explain hw each f the fllwing ins are made frm their neutral atm. Mg 2+ B 3 - S 2+ N 5-2. Frm the ins in questin 1, which is (as in ONLY ONE) the mst stable? Why? 3. What are the tw mst stable ins magnesium can make? 4. Frm yur answer t questin 3, which in des magnesium prefer t make? Explain. 27

28 Lab Activity - BUILD AN ATOM Objectives: 1. Make atm mdels that shw stable atms r ins. 2. Use given infrmatin abut subatmic particles t: a. Identify an element and its psitin n the peridic table b. Draw mdels f atms c. Determine if the mdel is fr a neutral atm r an in. 3. Predict hw additin r subtractin f a prtn, neutrn, r electrn will change the element, the charge, and the mass f an atm r in. Prcedure: 1. Direct yur web brwser t the PHET Build-an-atm simulatin at: Data/Results: - Make sure the fur chices n the right f the screen (Element, Symbl, Mass Number, Charge) are all expanded. The green + bx will expand the selectin, and the red bx will cllapse the sectin. - Under Mdel, select the radi buttn that says rbits. - Make sure the 3 chices at the bttm (Shw element name, Shw neutral/in, Shw stable/unstable) are all checked. - Nte that at any time yu can click the Reset All buttn in the bttm right crner. 2. Explre the simulatin. - Which particles are yu able t drag int the center? - What is the center called? 3. Ntice that as yu build yur atm, the name f the element will appear in the center, and the element symbl will be highlighted n the element sectin in the tp right. - What determines the name f the element yu build? 28

29 4. Ntice that as yu build yur atm, the wrd stable r unstable will appear in the center. - Identify 1 example f a stable atm and 1 example f an unstable atm in the table: STABLE Hw many prtns are in yur atm? Hw many neutrns are in yur atm What is the name f the element yu built? UNSTABLE - What seems t be a gd rule t make the center f the atm stable? 5. Ntice that as yu build yur atm, yu will see a red + In, black Neutral Atm r blue -In appear in the tp right. The charge is als indicated in the net charge sectin in the bttm right. The mass f the atm is indicated in the Mass number sectin n the right. In the table belw, check the clumns that wuld change as a result f adding r remving the stated particle. Name f Element Charge Mass Adding/remving prtn Adding/remving neutrn Adding/remving electrn - What is a rule fr making an atm with n charge (a neutral atm)? - What is a rule fr making an atm with a psitive charge (a psitive in)? - What is a rule fr making an atm with a negative charge (a negative in)? 29

30 - Identify 1 example each f a neutral atm, psitive in, and negative in in the table: NEUTRAL ATOM What is in yur atm/in? # prtns: Draw yur atm/in What is the charge? # neutrns: # electrns: POSITIVE ION # prtns: # neutrns: # electrns: NEGATIVE ION # prtns: # neutrns: # electrns: - What is a rule fr determining mass? 6. Design a psitive in with a charge f +2 Design a neutral stable atm with a mass and draw yur atm in the bx. f 9 and draw yur atm in the bx. # prtns: # neutrns: # electrns: Element name: Mass f in: # prtns: # neutrns: # electrns: Element name: Charge f in: 7. What can yu make with 4 prtns and 4 neutrns? A. Oxygen atm D. Beryllium atm B. Oxygen in E. Beryllium in C. Chices A & B F. Chices D & E 30

31 8. If yu have 5 prtns and 6 neutrns, hw many electrns wuld yu have t add t make a neutral atm? 9. What is the mass f an atm with 8 prtns 9 neutrns and 8 electrns? 10. If yu have 5 prtns, 6 neutrns, & 5 electrns, what wuld the element symbl lk like? 11. If yu have 8 prtns, 9 neutrns, 10 electrns, what wuld the charge be? A. Zer, it s an atm B. +2 in C. +1 in D. -1 in E. -2 in Cnclusin: Reflect n yur findings specifically discussing hw yu met the stated bjectives. 31

32 Lab Activity: Beanium Istpes Backgrund The nly research chemist at Anywhere High Schl has discvered a new element! This element was discvered in the mixture that makes up the baked beans in the cafeteria. The researchers have named this element Beanium. N tests have been dne n this element because the researchers culd nt determine the atmic mass f this new grund breaking element. There is a large sample f this new element in the lab at the research facility at the high schl. A reprter has learned that this tp secret facility is funded frm the same peple that fund AREA 51. As yu may knw, this secret funding cmes frm the internatinal alien cver-up cnspiracy started in Rswell, New Mexic in This lwly research chemist has brught this new element t yur classrm s that the lab technicians can determine the atmic mass f Beanium. Materials 100-mL beaker Sample f Beanium Prcedure The different istpes f Beanium are shaped like different types f beans. 1. Srt the Beanium sample int the different istpes. Recrd the number f each istpe in the data table prvided. 2. Find the mass f each istpe. This is nt the mass f ne atm, it is the mass f all the atms f that particular istpe. Recrd these masses in the data table. 3. Fllw the directins in the data table, and use yur vast knwledge f average atmic masses t find the atmic mass f Beanium. Results/Observatins Beanium Data Table: Use nly the three istpes with the greatest number f atms are t be recrded. (Any thers are impurities) Istpe #1 Istpe #2 Istpe #3 # f atms Ttal number f atms in yur sample (add up the # f atms f all 3 istpes) 32

33 Percent Abundance (# atms / ttal atms) (runded t nearest.01) Mass f Sample Mass f ne atm (mass f sample/ # f atms) (runded t nearest.01) Calculatins T find the atmic mass f Beanium, use the mass f ne atm f each istpe as the mass number and the percent f each istpe. Shw yur wrk belw: The atmic mass f Beanium is amu 33

34 Lessn 5: Bhr Diagrams Objective: T represent the atm using the mdel defined by Bhr. Lk at the mdel f the atm prpsed by Bhr (belw). We knw that the subatmic particle that determines the identity f the atm is the prtn and it is lcated in the nucleus. Des the identity f an atm ever change in chemical reactins? NO! S d yu think that the number f prtns ever changes in a chemical reactin? NO! Chemists might say then that the number f prtns is stable r nt changing. Nucleus Bhr did nt yet knw abut neutrns. These wuld nt cme until much later. Neutrns are als lcated in the nucleus f the atm. Atms f the same element may have different numbers f neutrns. These are knwn as istpes. Hwever, nce an atm has a specific number f neutrns, this number will nt change. Fr example, Cl-37 cannt give ne f its neutrns away t becme Cl-35! Thmsn had already discvered the electrn. Bhr s majr cntributin Since this subatmic particle is lcated n the utside f the atm, it is the subatmic particle that will have the mst impact n the prperties f the atms, because it is mst likely t be impacted by ther atms arund it. 34

35 Drawing Bhr Mdels f Atms A=P=E M - A = N Step 1: Calculate the number f prtns, neutrns and electrns using: A=P=E M - A = N Step 2: put prtns and neutrns in the nucleus, and electrns in the electrn shells. 1st energy level 2nd energy level 3rd energy level Let's Try a Cuple f Examples: D APE MAN fr Brn. Hw many prtns? neutrns? electrns? Did yu get 5 prtns, 6 neutrns, and 5 electrns? Did yu rund the mass befre subtracting? Draw Brn, putting the prper number f prtns (5) and neutrns (6) and electrns (5) in their prper places. D APE MAN fr Sdium. Hw many prtns? neutrns? electrns? Did yu get 11 prtns, 12 neutrns, and 11 electrns? Did yu rund the mass befre subtracting? Draw Sdium, putting the prper number f prtns (11) and neutrns (12) and electrns (11) in their prper places. 35

36 Flurine atm cnfiguratin 2-7 Fluride anin cnfiguratin

37 Electrn Cnfiguratins **All electrn cnfiguratins n theperidic Table are NEUTRAL (p + = e-) SUBSTANCE ELECTRON CONFIGURATION Magnesium Mg Brmine Br Barium *Lead * shrtcut allws yu t cut ut the first tw rbitals t shrten the address Valence Electrns: Kernel Electrns: inner electrns (all nn-valence electrns) Example: Sulfur Nitrgen: 2-5 Principle Energy Level (n) = electrn energy levels - each level can hld a maximum # f electrns Maximum # f electrns in an energy level = 2n 2 where n = quantum # (r perid #) Principle Energy Level (n) Maximum number f electrns (2n 2 ) Sample questin: What is the maximum number f electrns that can ccupy the 3 rd principal energy level in any atm? 37

38 Classwrk 2-5: Bhr Diagrams Objective: T represent the atm using the mdel defined by Bhr. 1. What subatmic particle is mst imprtant in determining the prperties f atms? Why? 2. Give the electrn cnfiguratins fr the fllwing: a. Carbn b. Strntium c. Flurine d. Argn e. Sdium f. Lithium 38

39 Bhr Mdel Practice Fr each element, write the ttal number f electrns n the line. Then clr the crrect number f electrns fr each rbit. Remember, fill the rbit clsest t the nucleus first, but never exceed the number each rbit can hld. Check the Peridic Table t find ut hw many electrns each element actually has. Sdium (Na) Ptassium (K) Hydrgen (H) Carbn (C) Silicn (Si) Oxygen (O) 39

40 Chlrine (Cl) Brmine (Br) Idine (I) Argn (Ar) Magnesium (Mg) Calcium (Ca) Nw draw yur wn Bhr mdel diagrams fr the fllwing atms: Lithium (Li) Sulfur (S) Nen (Ne) 40

41 Practice: Cnstruct Bhr diagrams fr the fllwing. Sme are neutral and sme are ins-be careful Carbn Flurine Beryllium He Li Ca 2+ Na + S 2- Argn Phsphrus Oxygen O 2- Aluminum Sdium N 3- He 41

42 Lessn 6: Electrns and Energy Objective: T relate energy state t electrn lcatin The mdern r quantum mechanical mdel f the atm describes energy levels as being further subdivided int sublevels and rbitals. The wrd rbital is ne yu need t knw, and simply refers t a regin f space arund the nucleus where there is a high prbability f finding an electrn. The mre electrns an atm has, the mre rbitals it will use. Each rbital cntains a maximum f 2 electrns. Each electrn in an atm has a particular amunt f energy depending n hw clse they are t the nucleus. Electrns in rbitals that are clser t the nucleus are mre energetically stable and are at a lwer energy. When all the electrns in an atm are in their lwest pssible energy levels, the atm is said t be in the grund state. The grund state electrn cnfiguratin is the ne displayed n the peridic table belw each element. When an atm interacts with an utside energy surce such as heat, light r electricity, the electrns can be affected. The mst accessible and therefre mst likely t be affected electrns are the valence electrns. If the electrn can absrb just the right amunt f energy t pp it t a higher energy level, it will indeed d this. The atm is nw described as being in the excited state. An atm in the excited state is unstable and will immediately emit the energy in the frm f light as the electrn(s) return t the grund state. The excited state cnfiguratin f an atm has the same number f electrns as the grund state. Fr example, xygen in the grund state is 2-6, but in the excited state might be 2-5-1, r 1-7, r In all cases the ttal number f electrns is that f an atm f xygen that is 8 electrns. Grund State = Excited State = grund state electrn cnfiguratin fr Li is 2-1 excited state electrn cnfiguratin fr Li culd be 1-2, S hw can yu tell if yu have a grund state r excited state cnfiguratin? 42

43 Bright Line Spectrum We need t cnsider the nature f light, r what is called the electrmagnetic spectrum. The electrmagnetic spectrum is a cntinuum f all electrmagnetic waves arranged accrding t frequency and wavelength. The sun, earth, and ther bdies radiate electrmagnetic energy f varying wavelengths. Electrmagnetic energy passes thrugh space at the speed f light in the frm f sinusidal waves. The wavelength is the distance frm wave crest t wave crest (see figure belw). Light is a particular type f electrmagnetic radiatin that can be seen and sensed by the human eye, but this energy exists at a wide range f wavelengths. The micrn is the basic unit fr measuring the wavelength f electrmagnetic waves. The spectrum f waves is divided int sectins based n wavelength. The shrtest waves are gamma rays, which have wavelengths f 10e-6 micrns r less. The lngest waves are radi waves, which have wavelengths f many kilmeters. The range f visible cnsists f the narrw prtin f the spectrum, frm 0.4 micrns (blue) t 0.7 micrns (red). HIGH ENERGY LOW ENERGY Grund à excited Grund ß Excited When atms absrb energy their electrns will shift t a higher energy level r an excited state. 43

44 This is a very unstable and temprary cnditin s the electrns will fall back dwn r drp t a lwer state energy level (r the grund state.) On the left f the diagram, electrns are shwn being excited frm the 2 nd energy level (n = 2) t the 3 rd, 4 th and 5 th energy levels. As they return t their riginal energy level (t the grund state), they emit their extra energy in the frm f a particular frequency (clr) f light. A spectrum f samples f unknwn cmpsitin can be bserved in rder t identify the elements present. Much f what we knw abut the structure and histry f the universe has been figured ut by bserving the spectra f stars. This diagram shws an example f hw a spectrum is taken and what it wuld lk like. Anther Resurce: (scrll dwn t Bhr Atm: Quantum Behavir f Hydrgen animatin) 44

45 Classwrk 2-6: Electrns and Energy Objective: T relate energy state t electrn lcatin 1. What is the relatinship between the distance an electrn is frm the nucleus, and its energy? 2. Hw des an atm enter the excited state? 3. What des an atm in the excited state d as its electrn(s) return t the grund state? 4. (T/F) When an atm becmes excited it lses electrns. 5. What is a Bright line spectrum? 6. Why d yu think that the bright line spectrum f an element can be thught f as a fingerprint fr that element? 7. The diagram shws the characteristic spectral line patterns f fur elements. Als shwn are spectral lines prduced by an unknwn substance. Which pair f elements is present in the unknwn? 1. lithium and sdium 2. sdium and hydrgen 3. lithium and helium 4. helium and hydrgen 45

46 Practice: Distinguish between grund state and excited state electrn cnfiguratins belw: Bhr Electrn Cnfiguratin Grund (G) r Excited (E) state? 1. Cmpared t a sdium atm in the grund state, a sdium atm in the excited state must have 1. a greater number f electrns 2. a smaller number f electrns 3. an electrn with greater energy 4. an electrn with less energy 2. Which principal energy level change by the electrn f a hydrgen atm will cause the greatest amunt f energy t be absrbed? 1. n = 2 t n = 4 2. n = 2 t n = 5 3. n = 4 t n = 2 4. n = 5 t n = 2 3. Spectral lines prduced frm the radiant energy emitted frm excited atms are thught t be due t the mvements f electrns 1. frm lwer t higher energy levels 2. frm higher t lwer energy levels 3. within their rbitals 4. ut f the nucleus 4. What is the electrn cnfiguratin f a sulfur atm in the excited state?

47 5. Electrn X can change t a higher energy level r a lwer energy level. Which statement is true f electrn X? 1. Electrn X emits energy when it changes t a higher energy level. 2. Electrn X absrbs energy when it changes t a higher energy level. 3. Electrn X absrbs energy when it changes t a lwer energy level. 4. Electrn X neither emits nr absrbs energy when it changes energy level. Chse frm the fllwing set f answers fr questins 10-12: Represents the electrn cnfiguratin f an atm f sdium in the grund state. 7. Represents the electrn cnfiguratin f the Na +1 in. 8. Represents an excited state electrn cnfiguratin fr an atm f sdium. 9. The characteristic bright-line spectrum f an element is prduced when its electrns 1. frm a cvalent bnd 2. frm an inic bnd 3. mve t a higher energy state 4. return t a lwer energy state 47

48 Lab Activity - Flame Tests Purpse: T understand that substances can be identified by flame clr. T learn hw we get light and clrs and understand what the atm is ding t prduce that light Safety Cncerns: Be sure t wear safety gggles and heat resistant glves Materials: Nichrme wire lp water 50mL beaker Heat resistant glves Prcedure: Cpper(II) sulfate Sdium chlride Lithium chlride Barium chlride Ptassium chlride Cpper chlride Strntium chlride Safety Glasses 1. Fill the 50mL beaker with water. 2. PROPERLY, light the Bunsen burner. Adjust the burner s that the flame is nly blue. 3. Dip the Nichrme wire in the water, and then int ne f the chemicals. Make sure that sme f the chemical adheres t the Nichrme wire, if it desn t dip the water in water and try again. 4. Hlding the burner at a slight angle place the wire in the flame and bserve the clr. Recrd yur data in yur CHART!! Be as specific as pssible abut the clr. 5. Mve t the next lab statin and repeat this prcedure 6. Repeat this prcedure until yu ve tested each chemical. 7. Remember t CLEAN UP!!! Data: Cmpund Cpper(II) sulfate Sdium chlride Lithium chlride Barium chlride Ptassium chlride Cpper chlride Strntium chlride Flame Clr Cnclusin/Questins: What is causing the metal-cntaining cmpunds t emit light? (Be sure t use the fllwing terms in yur answer: grund state, excited state) Use a diagram if necessary. 48

49 49

50 Emissin Spectra Data Light Surce : Clr f Light: Light Surce : Clr f Light: Light Surce : Clr f Light: Light Surce : Clr f Light: Light Surce : Clr f Light: Light Surce : Clr f Light: 50

51 51

52 Lessn 7: Lewis Dt Diagrams: Objective: T represent the atm using the mdel defined by Lewis The electrns are the subatmic particle that is mst imprtant fr ur study f Chemistry because it is n the utside f the atm and therefre it is the particle that is mst likely t be affected by ther atms arund it. Due t this, Chemist s use anther kind f diagram t help keep track f an atms electrns called a Lewis Dt Diagram. Lewis Dt Diagrams T find the number f valence electrns, yu start by writing dwn the electrn cnfiguratin X If yu are wrking with an in yu must adjust the valence electrns (add r subtract electrns) in the cnfiguratin befre cnstructing yur Dt Diagram be sure t draw yur final diagram with the initial charge n the in. An catin will always have brackets withut any electrns drawn inside and its charge utside n the tp right. A anin will always have all eight electrns drawn inside the brackets with its charge utside n the tp right. 52

53 Classwrk 2-7: Lewis Dt Diagrams Objective: T represent the atm using the mdel defined by Lewis. 1. Give the number f valence electrns fr the fllwing. a. Carbn b. Strntium c. Flurine d. Argn e. Sdium f. Lithium 2. Why are the valence electrns the mst imprtant electrns? 53

54 Cnstruct Lewis Dt diagrams fr the fllwing: Carbn Flurine Beryllium Br Li Ca 2+ Na + S 2- Argn Phsphrus Oxygen O 2- Aluminum Sdium N 3- He 54

55 Lessn 8: Article Analysis Objective: T relate the nature f science t histrical influences. Reading: Niels Bhr and Ernst Rutherfrd: The Life f a Scientist. Scientists are peple t and can lead very interesting lives. Just as ur childhd and envirnment mld us int wh we are, the life experiences f a scientist mld their character and ability t achieve greatness. Read the attached tw passages abut tw scientists that were instrumental in defining the structure f the atm. Answer the fllwing questins n a separate piece f paper t be cllected upn cmpletin f yur reading. 1. What type f educatin did bth scientists receive in their yuth and hw did it influence their careers? D they have anything in cmmn? 2. The wrk f ne scientist can very much influence the wrk f anther scientist. Hw des this statement apply t Bhr and Rutherfrd? Supprt yur answer with examples frm the passage. 3. Bth scientists lived and wrked during Hitler s reign. Hw did this influence their ability t cmplete their wrk? Supprt yur answer with examples frm the passage. 4. If Rutherfrd were still alive, what d yu think his reactin wuld be t the creatin f the atmic bmb and Bhr s rle in its creatin? 55

56 Niels Bhr Niels Bhr was brn and educated in Cpenhagen, Denmark. He lived, wrked, and died there, t. But his mark n science and histry was wrldwide. His prfessinal wrk and persnal cnvictins were part f the larger stries f the century. At the University f Cpenhagen, he studied physics and played sccer (thugh nt as well as his brther, wh helped the 1908 Danish sccer team win an Olympic silver medal). After receiving his dctrate in 1911, Bhr traveled t England n a study grant and wrked under J.J. Thmsn, wh had discvered the electrn 15 years earlier. Bhr began t wrk n the prblem f the atm's structure. Ernest Rutherfrd had recently suggested the atm had a miniature, dense nucleus surrunded by a clud f nearly weightless electrns. There were a few prblems with the mdel, hwever. Fr example, accrding t classical physics, the electrns rbiting the nucleus shuld lse energy until they spiral dwn int the center, cllapsing the atm. Bhr prpsed adding t the mdel the new idea f quanta put frth by Max Planck in That way, electrns existed at set levels f energy, that is, at fixed distances frm the nucleus. If the atm absrbed energy, the electrn jumped t a level further frm the nucleus; if it radiated energy, it fell t a level clser t the nucleus. His mdel was a huge leap frward in making thery fit the experimental evidence that ther physicists had fund ver the years. A few inaccuracies remained t be irned ut by thers ver the next few years, but his essential idea was prved crrect. He received the Nbel Prize fr this wrk in 1922, and it's what he's mst famus fr. But he was nly 37 at the time, and he didn't stp there. Amng ther things, he put frth the thery f the nucleus as a liquid drp, and the idea f "cmplementarity" -- that things may have a dual nature (as the electrn is bth particle and wave) but we can nly experience ne aspect at a time. In 1912 Bhr married Margrethe Nørlund. They had six sns, ne f whm, Aage, fllwed his father int physics -- and int the ranks f Nbel Prize-winners. Bhr returned t Denmark as a prfessr at the University f Cpenhagen, and in 1920 funded the Institute fr Theretical Physics -- spnsred by the Carlsberg brewery! Bhr remained directr f the institute fr the rest f his life, except fr his absence during Wrld War II. Bhr's persnal warmth, gd humr ("Never express yurself mre clearly than yu can think," he nce said), and hspitality cmbined with wrld events t make Cpenhagen a refuge fr 56

57 many f the century's greatest physicists. After Hitler tk pwer in Germany, Bhr was deeply cncerned fr his clleagues there, and ffered a place fr many escaping Jewish scientists t live and wrk. He later dnated his gld Nbel medal t the Finnish war effrt. In 1939 Bhr visited the United States with the news frm Lise Meitner (wh had escaped German-ccupied Austria) that German scientists were wrking n splitting the atm. This spurred the United States t launch the Manhattan Prject t develp the atmic bmb. Shrtly after Bhr's return hme, the German army ccupied Denmark. Three years later Bhr's family fled t Sweden in a fishing bat. Then Bhr and his sn Aage left Sweden traveling in the empty bmb rack f a British military plane. They ultimately went t the United States, where bth jined the gvernment's team f physicists wrking n atmic bmb at Ls Alams. Bhr had qualms abut the cnsequences f the bmb. He angered Winstn Churchill by wanting t share infrmatin with the Sviet Unin and supprting pstwar arms cntrl. Bhr went n t rganize the Atms fr Peace Cnference in Geneva in In additin t his majr cntributins t theretical physics, Bhr was an excellent administratr. The institute he headed is nw named fr him, and he helped fund CERN, Eurpe's great particle acceleratr and research statin. He died at hme in 1962, fllwing a strke. "An expert is a man wh has made all the mistakes which can be made, in a very narrw field." 57

58 Ernest Rutherfrd Ernest Rutherfrd's family emigrated frm England t New Zealand befre he was brn. They ran a successful farm near Nelsn, where Ernest was brn. One f 12 children, he liked the hard wrk and pen air f farming, but was a gd student and wn a university schlarship. After cllege, he wn anther schlarship t study at Cambridge University in England -- a turning pint in his life. There he met J.J. Thmsn (wh wuld sn discver the electrn), and Thmsn encuraged him t study recentlydiscvered x-rays. This was the start f a lng, prductive, and influential career in atmic physics. Rutherfrd eventually cined the terms fr sme f the mst basic principles in the field: alpha, beta, and gamma rays, the prtn, the neutrn, half-life, and daughter atms. Several f the century's giants in physics studied under him, including Niels Bhr, James Chadwick, and Rbert Oppenheimer. Early n he fund that all knwn radiactive elements emit tw kinds f radiatin: psitively and negatively charged, r alpha and beta. He shwed that every radiactive element decreases in radiactivity ver a unique and regular time, r half-life, ultimately becming stable. In 1901 and 1902 he wrked with Frederick Sddy t prve that atms f ne radiactive element wuld spntaneusly turn int anther, by expelling a piece f the atm at high velcity. Many scientists f the day scrned the idea as alchemy. They stuck with the age-ld belief that the atm is indivisible and unchangeable. But by 1904 Rutherfrd's publicatins and achievements gained recgnitin. He was an extremely energetic researcher: in the span 58

59 f seven years, he published 80 papers. In 1907 he went t the University f Manchester and with Hans Geiger (f the Geiger cunter) set up a center t study radiatin. In 1909 he began experiments that were t change the face f physics. He discvered the atmic nucleus and develped a mdel f the atm that was similar t the slar system. Like planets, electrns rbited a central, sun-like nucleus. Acceptance f this mdel grew after it was mdified with quantum thery by Niels Bhr. Fr his wrk with radiatin and the atmic nucleus, Rutherfrd received the 1908 Nbel Prize in chemistry. He was slightly put ut, since he was a physicist and felt a bit superir t chemistry! In 1914 Rutherfrd was knighted. During Wrld War I, he left his research t help the British Admiralty with prblems f submarine detectin, but was sn back in the lab. He managed t prduce the disintegratin f a nn-radiactive atm, disldging a single particle. The particle had a psitive charge, s it must have cme frm nucleus: he called this new particle a prtn. With this experiment, he was the first human t create a "nuclear reactin," thugh a weak ne. In 1919 he tk ver as directr f the Cavendish Labratry. His warm, utging persnality made him an utstanding mentr t researchers attracted there by his scientific achievements. He tk n mre supervisin and less direct research as years went by. In 1931 he was made the first Barn Rutherfrd f Nelsn, allwing him t jin the Huse f Lrds. He was fiercely anti-nazi, and in 1933 he served as president f the Academic Assistance Cuncil, established t help German refugees. He wuld nt persnally help chemist Fritz Haber, hwever, wh had been instrumental in creating chemical weapns in Wrld War I. Rutherfrd died tw years befre the discvery f atmic fissin. "All science is either physics r stamp cllecting." 59