Periodic Properties Chapter 12 Notes

Valence Electrons Valence electrons – Electrons in the outer energy level that can be lost, gained, or shared (connected to the group #) Valence electrons – Electrons in the outer energy level that can be lost, gained, or shared (connected to the group #) Group # Valence e

Atomic Radii The atomic radius is a measure of the size of an atom (½ distance betw 2 nuclei). The larger the radius, the larger is the atom. alchemistry/flash/atomic4.swfhttp:// alchemistry/flash/atomic4.swf 8http:// 8

Atomic Radii Radii decrease across a period because the nucleus gets a larger positive charge Radii decrease across a period because the nucleus gets a larger positive charge Radii increase down a group because the nucleus gets larger Radii increase down a group because the nucleus gets larger Which is larger and why? Which is the smallest? Li, O, C, or F Which is larger and why? Which is the smallest? Li, O, C, or F Largest: LiSmallest: F Largest: LiSmallest: F What about Be, Mg, Ca, or Sr? What about Be, Mg, Ca, or Sr? Largest: Sr Smallest: Be Largest: Sr Smallest: Be

Ionization Energy Ion – an atom that has a positive or negative charge Ion – an atom that has a positive or negative charge Ionization – process that results in forming an ion Ionization – process that results in forming an ion Ionization energy (IE) – energy required to remove one electron from a neutral atom (energy needed to make a positive charge) Ionization energy (IE) – energy required to remove one electron from a neutral atom (energy needed to make a positive charge)

Ionization Energy A + Energy A + + e - IE increases across a period because the nuclear charge increases (more electrons in the orbitals) IE decreases down a group because it is easier to remove e - from higher energy levels

Electron Affinity Electron Affinity (EA) – energy needed to add an electron to a neutral atom (opposite of IE). Electron Affinity (EA) – energy needed to add an electron to a neutral atom (opposite of IE). A + e - A - + energy

Electron Affinity EA increases across periods ( EA increases across periods ( EA decreases down groups as nuclear charge increases. EA decreases down groups as nuclear charge increases. ***There are many exceptions to this rule!!!

Ionic Radii Cation – positive ion (decrease in atomic radii) Anion – negative ion (increase in atomic radii) Ionic radii increase across periods because the electron cloud expands Ionic radii increase down groups as energy levels increase

Electronegativity Electronegativity -- the ability of an atom to attract electrons Electronegativity -- the ability of an atom to attract electrons Electronegativities increase across a period and decrease down groups (but there are exceptions!) Electronegativities increase across a period and decrease down groups (but there are exceptions!) **Fluorine is the most electronegative atom!!

The Best Way to Remember…. Just know all the trends that surround Fluorine, and work your way down or across! Just know all the trends that surround Fluorine, and work your way down or across! F – most electronegative, highest IE, highest EA, small atomic and ionic radii F – most electronegative, highest IE, highest EA, small atomic and ionic radii

All Periodic Trends