Trends of the Periodic Table I. Oxidation Numbers (p. 222) II. Reactivity III. Atomic Radius (pp ) IV. Ionization Energy (pp ) V. Electronegativity (pp )

I. Oxidation Numbers An oxidation number is the charge of a monatomic ion. Oxidation numbers are based on the valence electrons that an element will lose OR gain to have a full outer energy level. Notice the trend on the periodic table...

II. Reactivity A. The trend: for metals-- 1. across a period the reactivity decreases; 2. down a group the reactivity increases –The rationale... B. The trend: for non-metals-- 1. Across a period the reactivity increases; 2. down a group the reactivity decreases –The rationale...

III. Atomic Radius The trend: (1) across a period the radius decreases (2) down a group the radius increases The rationale: Increasing positive charge in the nucleus and negative charge in the electron cloud causes an increased attraction and therefore a shorter distance. More electrons between the nucleus and the valence electrons weaken the attraction between them, thereby allowing a wider gap.

Atomic Radius for IONS The trend: (1) positive ions are always smaller than their neutral counterparts (2) negative ions always become larger than their neutral counterparts The rationale: The particles found in greatest number have the greatest force: –if there are more protons than electrons (pos’ve), the nucleus pulls them in; –if there are more electrons (neg’ve), they repel each other enough to move farther away from the nucleus

IV. Ionization Energy The energy required to remove an electron OR how strongly an atom holds on to its valence electrons The trend: (1) across a period the IE increases (2) down a group the IE decreases The rationale: As you move across the PT, atoms are less willing to give e - up and actually want them more (they have an increasing hold on val. e - ) as you go down a group, the increasing size of atoms allows the hold on valence e - to be weaker, therefore decreasing IE

V. Electronegativity (pp , ) The relative ability of the element to attract electrons in a chemical bond (how bad it’s pulling for another electron) The trend: (1) across a period the EN increases (2) down a group the EN decreases The rationale: across a period, elements are more ‘interested’ in gaining electrons because that helps them be closer to the noble gases; down a group the shielding factor means an element ‘cares’ less about gaining another electron

V. Electronegativity (pp , ) Helpful hint: Fluorine is the most EN element! (remember: the T-Rex of the PT) EN values can help you predict the bonding character in a compound. difference in EN values: Ionic 1.7 < x < 4 Polar Covalent 0.5 < x < 1.7 Covalent (non-polar)0 < x < 0.5

V. Electronegativity & Bonding Ionic bonds result when one element is WAY MORE EN than the other…(big difference in EN values) His EN: _______ Her EN: Diff.: Na F

V. Electronegativity & Bonding Polar Covalent Bonds result when one element has a greater EN value than the other, but not so great of a difference as in ionic bonds His EN: _______ Her EN: Diff.: O H

V. Electronegativity & Bonding Covalent bonds occur when the EN values are REALLY similar. The affinity for electrons is almost equal, so they are in ‘gridlock’… they must share their e - ; there’s no clear-cut ‘winner’ Red EN: _______ Blue EN: Diff.: C S

Summary for Trends increasesdecreases increases decreases increases decreases Reactivity AR EN IE