Download Periodic Trends

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!!!
Getting larger
Getting larger
Which is the larger atom?
S or O?

S because its valence
rd
3
electrons are on the
EL while O’s are on the
nd
2 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
rd
the 3 EL while N is
nd
on the 2 EL