1. Atomic and Ionic radius 2. Ionization energy 3. Electronegativity 4. Electron Affinity PERIODIC TRENDS

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1 PERIODIC TRENDS Nov 11 9:05 PM Periodic trends that change in a predictable way: 1. Atomic and Ionic radius 2. Ionization energy 3. Electronegativity 4. Electron Affinity Nov 11 8:20 PM 1

2 Atomic Radius * atoms do not have definable edges * influenced by electron configuration * defined by how closely an atom lies to a neighboring atom * atom sizes can change depending on what they're bonded with Metallic radius is for METALS = one half the distance between two adjacent atoms in a crystal Covalent radius is for NONMETALS = half the distance between 2 identical atoms in a bond Nov 11 8:23 PM 200 pm 100 pm = atomic radius Nov 19 9:43 PM 2

3 Going left to right across a period......atoms tend to get smaller. Nov 11 8:30 PM Going down a family, atoms tend to get BIGGER. Nov 11 8:31 PM 3

4 WHY? ATOMIC RADIUS DECREASES AS YOU MOVE ACROSS THE PERIODS *Increasing positive nuclear charge shrinks the cloud * Principal energy level remains the same (electrons added to the same orbitals in same energy level) * No shielding ATOMIC RADIUS INCREASES AS YOU MOVE DOWN A FAMILY * Because electrons are filling sublevels located in higher energy levels that are farther from the nucleus, the atoms get bigger. * Shielding effect. d 10 Ga < Al because the greatly increased nuclear charge is shrinks the atom more than the 10 electrons make it bigger. Nov 19 9:54 PM The inner core electrons shield the valence electrons from the inward pull of the nucleus. Nov 11 8:42 PM 4

5 SHIELDING EFFECT Nov 19 10:22 PM IONIC RADIUS An ion is a charged particle and can be positive or negative. 1. Metals form cations. 2. Cations are positive. 3. Cations are smaller than their parent atoms. Nov 11 8:43 PM 5

6 * valence electron is lost leaving an empty outer orbital * electrostatic repulsion between electrons and nucleus decreases = remaining electrons are pulled closer Nov 11 9:14 PM 1. Nonmetals gain electrons. 2. Anions are negative. 3. Anions are bigger than their parent atoms. Sulfur atom S 2- Sulfide ion [Ne] 3s 2 3p 4 [Ne] 3s 2 3p 6 increased electrostatic repulsion Nov 11 8:50 PM 6

7 Nov 11 9:03 PM Atomic and Ionic Radii Comparison Nov 11 8:46 PM 7

8 Nov 11 8:49 PM Ionization Energy kj/mole Ionization energy: the energy required to remove an electron from a gaseous atom. * an endothermic process It is a measure of how difficult it is to remove the most loosely held electron from an atom in the gaseous state. Nov 19 10:00 PM 8

9 Low IE = easier to remove an electron (metals) High IE = harder to remove an electron (nonmetals) Nov 11 9:19 PM INCREASE Increases as you go across a period Increases as you go up a family * Electrons are closer to the nucleus * less shielding effect Increased nuclear charge Nov 19 10:00 PM 9

10 Ionization Energy Nuclear charge - increase charge, increase IE Shielding Effect - increase shielding effect, decrease IE Radius - increase radius, decrease IE Sublevel - removing an e - from a full or ½ full sublevel requires more energy Nov 11 9:21 PM IE 2 and IE 3 With enough energy, electrons can be removed from cations as well. Each extra e - removed feels a stronger nuclear charge. 3s 1s 2s 2p Nov 11 9:22 PM 10

11 How do you know when to stop if you don't have this table? OCTET RULE: atoms tend to lose, gain or share electrons in order to get a full set of 8 valence electrons Nov 11 9:24 PM Electron Affinity I e *energy given off when a neutral atom in the gas phase gains an extra electron to form a negatively charged ion * exothermic process Nov 2 3:22 PM 11

12 Electronegativity a measure of the ability of an atom in a molecule to draw bonding electrons to itself Determined by Linus Pauling in 1932 Dimensionless Fluorine is the most electronegative Francium is the least Nov 2 3:23 PM Nov 2 3:37 PM 12

13 Oct 30 7:46 AM Nov 11 4:17 PM 13

14 Nov 11 9:30 PM 14

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