Valence electrons These are the electrons on the outermost ring. They are available for bonding. They can be found by counting the columns on the Periodic.

Valence electrons

These are the electrons on the outermost ring. They are available for bonding.

They can be found by counting the columns on the Periodic Table.

EX: P in group 5A = 5 valence electrons

Common Ion In order to be stable, all elements want an

electron configuration of a NOBLE GAS. They will gain or lose electrons to complete

their outside shell. The periodic table will help you to be able to

predict this.

Atomic Size

Atomic Radius – the distance from the center of an atom’s nucleus to its outermost electron

Atomic Radius Trends:1. Atoms get larger as you

move down a group

WHY? As you move down a group, the valence electrons are on higher principle energy levels which are further from the nucleus

2. Atoms get smaller as you move from left to right across a period

WHY? As you move from left to right across a period there are more protons pulling the electrons in more closely causing it to be smaller

If your trends contradict each other, always use the PRINCIPLE ENERGY LEVEL TO DECIDE!!!

Gettin

g la

rger

Getting larger

Which is the larger atom?

S or O? S because its valence

electrons are on the 3rd EL while O’s are on the 2nd EL

Which is the larger atom?

C or O?C is because they are on

the same EL so the one with fewer protons will be larger (less pull from the nucleus)

Which is the larger atom?

N or S?

S because it is on the 3rd EL while N is on the 2nd EL