Periodic Trends. 1. (#2 3a) I can determine how gaining or losing electrons affects the atomic

Transcription

1 Periodic Trends objectives: (#2 3) How do the properties of electrons and the electron shells contribute to the periodic trends? 1. (#2 3a) I can determine how gaining or losing electrons affects the atomic radius justified by Coulomb's Law and orbital structure. 2. (#2 3b) I can determine how gaining or losing protons affects the atomic radius justified by Coulomb's Law and orbital structure. 3. (#2 3c) I can determine how gaining or losing electrons affects the ionization energy justified by Coulomb's Law and orbital structure. 4. (#2 3d) I can determine how gaining or losing protons affects the ionization energy justified by Coulomb's Law and orbital structure. 5. (#2 3e) I can determine whether an atom is more or less reactive then another justified by Coulomb's Law and orbital structure. Atomic Radius Ionization Energy Reactivity Oct 4 5:28 AM 1

2 Coulomb's Law basis stability of atoms and ions and periodic trends 2 variables: distance and charges Distance: Charge: The greater the charges are, the stronger the force of attraction F = Force q = charge of a particle, need + and to attract r = radius (distance) k = constant Oct 15 1:31 PM 2

3 Atomic Radius Distance between center and outer electron What do the radii of atoms compare as you move down the periodic table? As you go down the PT, every row adds an energy level, so the radius will be bigger Which atom has largest radius? Why? C(#6) Si(#14) Sn(#50) Sn(#50), more energy levels or shells Oct 4 5:28 AM 3

4 What happens to the radius as you add electrons across the row? Across the PT same valence shell, (left to right) More and p + increase attraction (pulling) in same valence shell, so the radii will decrease Why? Coulomb's Law: charges increase, have greater attraction (and held closer) 3p + 4p + 5p 6p e 4 Li Be B C #3 #4 #5 #6 5 6 Which is bigger? Why? S(#16) or Ar(#18) S(#16) is bigger: same valence shell, more attraction (Coulomb's Law) between 18p + and 18 than 16 p + and 16 Which atom is the biggest on the PT? Fr(#87) Coulomb's Law: Distance: most valence shells Charges: only one valence shell so less attraction than if more in the shell Oct 4 5:28 AM 4

5 Atomic Radii Trend: increase as you go to the left smallest atoms here increase as you go down biggest atoms here Oct 4 5:28 AM 5

6 periodic trends 2015.notebook Atomic Radii Graph shows trends Why does the radius increase from H, to Li, to Na, to K to Rb? These are all Alkali Metal family atoms, and each new row is a new energy level, (each new shell increases the radius) Why does the graph decrease after each alkali metal? Electrons are added as you go across the period, increasing effective nuclear charge which gives greater attraction ("hug" in closer) and decreased radius of the atom Oct 4 5:28 AM 6

7 Oct 8 8:42 AM 7

8 Oct 8 8:42 AM 8

9 Reactivity atom is reactive atom is not reactive valence shell not full are easily gained or lost Metals like to lose electrons. Li Li + Full valence shell=stability lowest energy state I'm full! noble gases Non metals like to gain electrons F F Oct 5 2:36 PM 9

10 Metal reactivity analogy *Proximity (distant more reactive) boy Li girl this is close to the nucleus and has a stronger attraction girl e e e Fr e boy Oct 5 2:36 PM 10

11 Metal reactivity analogy boy Li girl this is close to the nucleus and has a stronger attraction and no "distractions" *Proximity (distant more reactive) *Shielding (decrease effective nuclear charge) distractions girl e e e Fr e boy Oct 5 2:36 PM 11

12 difference between metals and non metals lose gain Reactivity of metals Metals lose electrons. Therefore, the farther away the is, the easier it is to lose and the more reactive it is less reactive Li Fr more reactive Alkali Metals (Gp1) Vs. Akaline Earth Metals (Gp2) 3p + 4p + 3 Li Be #3 #4 4 Li (Gp 1) is more reactive than Be (Gp 2) Li is less attracted to nucleus than Be easier (less energy) to lose 1 on Li Coulomb's Law Distance and Charge more reactive Oct 5 2:36 PM 12

13 Reactivity of Non metals Non metals gain. Therefore, the closer the is, the easier it is to gain and the more reactive it is. more reactive noble gases are not reactive F more reactive I e 8p + 9p O F #8 #9 F (Halogen) is more reactive than O is attracted to F nucleus easier (less energy) to gain 1 on F Coulomb's Law Distance and Charge less distance and more charge more reactive noble gases are not reactive Oct 5 2:36 PM 13

14 Reactivity Summary most reactive nonmetal F noble gases are not reactive Fr most reactive metal Oct 4 9:12 PM 14

15 Ionization Energy Amount of energy needed to remove an. Amount of energy needed to remove succeeding always requires more energy. Pulling a negative away from a positive is more difficult. (requires more energy) Which family on the PT needs the most energy to remove (highest ionization energy?) noble gases Which family on the PT requires the least energy to remove (lowest ionization energy?) Alkali Metals Oct 5 2:36 PM 15

16 Ionization Energy With what we know about reactivity, what electrons would be easiest to remove? Easiest to remove Metals (want to lose ) Atoms where are the farthest away. (larger radius) 1st electron removed (Group 1 Alkali Metals) Hardest to remove Non Metals (want to gain ) Atoms where those are the closest. (Noble gases and smallest radius) He Most Ionization energy Hardest to remove Easiest to remove least ioniation energy Fr Oct 5 2:36 PM 16

17 Ionization energy summary What is the trend? most IE least IE Oct 5 2:36 PM 17

18 1. Metals tend to (gain/lose?) electrons 2. Nonmetals tend to (gain/lose?) electrons 3. Which atom has the bigger radius? Why? a. Mg (#12) or Cl (#17) b. Mg(#12) or Ra (#88) 4. Which atom is more reactive? Why? a. K(#19) or Ca (20) b. Mg(#12) or Ra (#88) c. Cl (#17) or F(#9) 5. Which atom has the smaller ionization energy? Why? a. K(#19) or Ca (20) b. Mg (#12) or Cl (#17) c. Mg(#12) or Ra (#88) Oct 15 10:40 AM 18

19 1. Metals tend to (gain/lose?) electrons 2. Nonmetals tend to (gain/lose?) electrons 3. Which atom has the bigger radius? Why? a. Mg (#12) or Cl (#17) b. Mg(#12) or Ra (#88) (same energy level for both) Cl has greater charge, more Coulombic Force, electrons are "held closer" 4. Which atom is more reactive? Why? a. K(#19) or Ca (20) b. Mg(#12) or Ra (#88) c. Cl (#17) or F(#9) 5. Which atom has the smaller ionization energy? Why? a. K(#19) or Ca (20) b. Mg (#12) or Cl (#17) c. Mg(#12) or Ra (#88) Oct 15 10:40 AM 19

20 periodic trends 2015.notebook First Ionization Energy Graph Oct 4 5:29 AM 20

21 Removing succeeding electrons First electrons are always the easiest electrons to remove. Why did the ionization energy spike at different times? Na: 1 Valence electron Mg: 2 Valence electrons Al: 3 Valence electrons After clearing out a shell it is very difficult to break into a full shell. Oct 6 6:44 AM 21

22 Ionic Radii What happens to the radius if electrons are lost? Metal cations lose whole shell 11p 12n Na atom lose 1 e e e 11p e e 12n 11p + 11p + 11e Na shells, larger 2 shells, smaller What happens to the radius if electrons are gained? Nonmetal Anions gain electrons. e 16p S atom 16p + 16 gain 2 e 16p S 2 ion 16p + 18 Proton "beacon" is the same force of attraction Extra electrons will repel each other, slightly increasing the radius Isoelectronic Comparison of ion radii: 8 p + 9 p + 10 p + 11 p + 12 p + all have 10 electrons the charge increase, therefore the Coulomic Force increases, electrons are closer and the radius is smaller Oct 8 7:50 AM 22

23 Al Ca 2+ Ne O O 2 Ba He Ar 1) When assessing which atom is bigger what is the FIRST THING I LOOK FOR? 2) Have any atoms here lost or gained an energy level due to ionization? 3) List all atoms working in the same energy level in groups. 4) When trying to discriminate between small differences in size (atoms in a. More protons will always make you? b. If you have the same number of protons, adding electrons will alway 5) List the atoms above in order of increasing size. 6) List these atoms above in order of increasing ionization energy. 7) Y: 1s 2 2s 2 2p 6 3s 1 X: 1s 2 2s 2 a. Which atom is biggest, X or Y b. This atoms biggest energy level on the biggest atom is? c. How many valence electrons do each of these have? d. Draw a Bohr Diagram of each. Oct 8 8:37 AM 23

24 Periodic Trends Practice Al Ca 2+ Ne O O 2 Ba He Ar 3 3 1) When assessing which atom is bigger what is the FIRST THING I LOOK FOR? number of energy levels, (distance) 2) Have any atoms here lost or gained an energy level due to ionization? Ca +2 3) List all atoms working in the same energy level in groups. 4) When trying to discriminate between small differences in size (atoms in the same energy level) a. More protons will always make the radius smaller. because there will be more Coulomic Force holding the electrons closer to the nucleus b. If you have the same number of protons, adding electrons will always the radius bigger. O O 2 8 p 8 e 8 p 10 e larger more repel each other and spread out 5) List the atoms above in order of increasing size. He Ne O O 2 6) List these atoms above in order of increasing ionization energy. Ba Al Ar O 2 O Ne He 56p 56e 7) Y: 1s 2 2s 2 2p 6 3s 1 X: 1s 2 2s 2 a. Which atom is biggest, X or Y b. This atoms biggest energy level on the biggest atom is? the 3rd energy level Ca +2 Ar c. How many valence electrons do each of these have? X has 1 valence electron, Y has 2 valence electrons d. Draw a Bohr Diagram of each. Al Ba 1st 2nd 3rd 6th 13p 13e 18p 18e Ca +2 20p 18e 8p 10e 8p 8e 10p 10e 2p 2e e e e Y X Oct 8 8:37 AM 24

25 Sample questions for quiz: 2 factors of Coulomb s law? Which element is bigger? Explain with Coulomb's Law. Li or B? O or S? Which element has lower IE? Explain with Coulomb's Law. Li or B? O or S? Why does Cesium have a low ionization energy? (use Coulomb s law!) Why does Neon have a high ionization energy? (use Coulomb s law!) Nov 6 7:55 AM 25

26 Sample questions for quiz: 2 factors of Coulomb s law? distance and charge Which element is bigger? Explain with Coulomb's Law. oli or B? Li has 3 p, 3 e B has greater charge, o B has 5 p,5 e O or S? O outer are in the 2nd energy smaller level and S outer are in the 3rd energy level Which element has lower IE? Explain with Coulomb's Law. o Li or B? O or S?o Charge 3rd level has a greater radius than 2nd Li has 3 p, 3 e B has 5 p,5 e greater Coulomic attraction of to p +, so B is B has greater charge, greater Coulomic attraction of e to p, so Li requires less energy to lose e than B does O outer are in the 2nd energy level and S outer are in the 3rd energy level so S requires less energy to lose an than O because S are at a greater distance Why does Cesium have a low ionization energy? (use Coulomb s law!) easy to pull off e Distance large (big radius, many energy shells) less attraction small, low attraction Why does Neon have a high ionization energy? (use Coulomb s law!) Distance small, great attraction of outer e to nucleus difficult to pull off Charge large great attraction high attraction of valence e to nucleus Nov 6 7:55 AM 26