Unit 3 - The Periodic Table

Transcription

1 Unit 3 - The Periodic Table Unit Objectives - At the completion of this unit you will be able to: Describe the origin of the periodic table State the modern periodic law Explain how an element s electron configuration is related to the element s placement within a period and a group on the periodic table State the trends of the following properties within periods and groups of elements including: Ionization energy Electronegativity Atomic Radius Reactivity Metallic/Nonmetallic character Identify and state the properties of the following groups in the periodic table: Alkali metals Alkaline earth metals Halogens Noble Gases Transition elements Locate within the periodic table and state the properties of the metals, nonmetals, and metalloids (semi-metals) 1

2 Dimitri Mendeleev Developed the first Arranged elements according to ascending Grouped elements by similar Predicted the existence and properties of new Notice the gaps and how few elements there were Henry Moseley English physicist who determined the number of in the nucleus by measuring the wavelength of X-rays given off by certain metals. Developed the first concept of 2

3 Chemical Periodicity/History of the Table: Periodic = cyclic; repeating patterns/cycles; similar to monthly/weekly calendar (days of the week) Ex: tired on Mondays, happy on Fridays Dmitri Mendeleev (Russia) 1 st chemist to arrange newly found elements into a table form/usable manner Elements arranged according to Resulted in or periodic intervals being *Henry Moseley (England) Arranged table by (or # of protons) which proved to be much more effective How the modern day periodic table is arranged Periodic Law = elements in periodic table are functions of their Arrangement of the Periodic Table: The Periodic Table is made up of periods and groups: Periods = (run left to right) on Periodic Table # of period tells us the (AKA principal energy level) properties of elements change drastically (metals metalloids/semi-metals nonmetals) # of increases from left to right (1 8) Ex: K is in period 4 3

4 Groups = (run up & down) on Periodic Table; each group contains the same # valence electrons & (not identical) chemical/physical properties K is in Group 1 Let s look at the LEWIS DOT DIAGRAMS/electron configurations elements in the same group H = Li = Na = K = Rb = Cs = Fr = What similarities can you observe within the above electron configurations? All have valence electron Group # = Period number = OCTET = full (8 electrons, except for elements) 4

5 The Groups: Group 1 ALKALAI METALS ( ) All have valence electron Easily their one electron to become ions reactive never found alone in nature Contains the reactive metal: Probably, but it s so rare, we ve got to go w/ Group 2 ALKALINE EARTH METALS ( ) All have valence electrons Prefer to their two electrons to become ions reactive never found alone in nature Groups 3-12 TRANSITION METALS Found in the of the table (the D block) Form in solution (ex: Cu is bright blue when dissolved in water) Tend to be will lose electrons or gain them depending on what other are present group of metals Groups BCNO groups (not a single group) groups Metals, nonmetals, & metalloids found along the staircase (many different properties) 5

6 Group 17 HALOGENS (FAMILIY) valence electrons Like to gain electron to become ions with charge (8 is great!) Form called Contains the most : All making up the group Three states of matter found in group: Ex: Group 18 NOBLE GASES (FAMILY) or Have ( e- in valence shell/outer energy level) Most group; exist in nature Exception to the is (only has valence e-) EVERYONE WANTS TO BE A NOBLE GAS & HAVE 8 ELECTRONS! 8 IS GREAT! Ex: Hydrogen Not officially part of a group Both a and a can be seen as The Lanthanide/Actinide Series two rows on bottom of table (detached) Elements & Actually belong to the 6

7 The Periodic Table can be keyed for many things! The Staircase 1. metals: make up of table of or staircase except STP (except ) (can be hammered/molded into sheets) (can be drawn/pulled into wire) have (are shiny) good (allow heat & electricity to flow through them) due to their valence e - like to e - to form ions 2. nonmetals: of or staircase mostly STP except malleable/ductile; (shatter easily) luster ( ) or conductors like to e - to form ions 3. metalloids (AKA semi-metals): have properties of both & staircase (bet. & on table) except 7

8 STATES OF MATTER (at STP) 1. solids(s) most elements are solids at STP; ex: a. Definite b. Definite 2. liquids (l) only TWO elements at STP (Br & Hg); ex: a. Definite b. Takes the of the container 3. gases (g) H, N, O, F, Cl, & all of group 18 (noble gases); ex: a. No definite b. their container 8

9 Diatomic Elements (7UP) Siamese Twins Elements that can t exist in nature Travel in Too to stand alone Contain 2 atoms 8 of them must memorize! Use 7-UP trick (see below) Include the following elements: o N 2, O 2, F 2, Cl 2, Br 2, I 2 (make the shape of a ) o UP H 2 Example: Nitrogen (when by itself) can only exist as N 2. You will never see nitrogen by itself (not paired) Allotrope = 1 of 2 or more different of an element (nonmetal) in the same, but with different and different / properties Ex: allotropes of oxygen vs. Ex: allotropes of carbon (in your pencil) vs. 9

10 Periodic Table Trends 1. Atomic Radius = ½ the distance between neighboring of a given Going down a group, atomic radius increases Reasons: MORE orbitals/energy levels take up MORE space SHIELDING electrons from inner energy levels interfere/block nucleus from valence electrons Going across a period, atomic radius decreases Reasons: getting (more P & N) charge is e - (remember they are light) are being pulled in, filling orbital to maximum capacity Ionic Radius (Atomic radius for ions): If you e -, radius Reason: Same charge pulling on e - nucleus has pull on outermost e - If you e -, radius Reason: Same charge pulling on e - nucleus pulls e - 10

11 2. Ionization Energy = amount of needed to the most bound e - from and atom/ion in the phase (values for each element listed in Table S) ( with electrons) Metals Nonmetals X + energy Going down a group, ionization energy DECREASES Reasons: as you go down a group, e - are from the remove e- in shells the from the e- Going across a period, ionization energy INCREASES Reasons: e - are being pulled to the (increased ) more needed to remove an e - 11

12 3. Electronegativity: of ionization energy desire to e - of an atom/ion for e - (values for each element listed in Table S) (GREEDY for electrons) Electronegativity values range from to The electronegative element on the Periodic table is ( ) The electronegative elements on the Periodic table are or ( ) Going down a group, electronegativity Reasons: Add one energy level shells the from the electrons Harder for to attract additional e- *Shielding Going across a period, electronegativity Reason: heading across a period you are reaching the so desire to electrons increases (8 is great!) 12

13 4. Reactivity = or of an element to go through a change (or w/ another element) (*Can NOT compare metals to nonmetals) Metals: (recall: the most reactive metal is ) Going down a group, reactivity (for ) Reason: Increased means e - are held less tightly e - more easily Going across a period, reactivity (for ) Reasons: Increased nuclear and pulls more tightly on tiny, negative e - to remove e - (magnet vs. car analogy) Nonmetals: (recall: the most reactive nonmetal is ) Going down a group, reactivity (for ) Reason: Increased for nucleus to attract more valence e - Going across a period, reactivity (for ) Reason: Increased nuclear & for nucleus to attract more valence e - 13

14 Isoelectronic: atoms or ions that have the SAME number of ELECTRONS Ex: F -, Ne, and Na + all have 10 electrons 14