I II III

The Periodic Trend

size of atom

Atomic Radius

0

50

100

150

200

250

0 5 10 15 20Atomic Number

Ato

mic

Ra

diu

s (

pm

)

Atomic Radius - Groups

Atomic radius increases as you move down a group

Why?Atomic size increases

because more electrons are added which results in more orbits.

Atomic Radius - Periods

Atomic radius decreases as you move across a period

Why?Increased (+) nuclear charge pulls the (-)

electrons closer to the nucleusAtomic size decreases

1

2

3

4 5

6

7

Increases to the LEFT and DOWN

Atomic Radius

IONIC RADIUS

Ions are charged atoms, either +ve or –ve

Cations are +ve and form when atoms lose electrons

Anions are -ve and form when atoms gain electrons

Ionic Radius – Cations Group

Cations are smaller than their parent atoms.

Why?By losing electrons they

become shorter

Ionic Radius – Anions Groups

Anions are larger than their parent ions

Why?When extra (-) electrons

are added, the size of atom becomes bigger.

ELECRTONEGATIVITY

Ability of an atom to attract electrons toward itself in a chemical bond.

The difference between the electronegativities of two atoms determines what kind of bond they form.

Electronegativity - Periods

Electronegativity increases going left to right across the periodic table.

Fluorine has the highest. Lithium has the lowest.

Li Be B C N O F

1.0 1.5 2.0 2.5 3.0 3.5 4.0

Electronegativity - Groups

Electronegativity decreases going down a group

WHY??As atoms get bigger the

bonding electrons are far from the attraction of the nucleus.

H 2.1

Li 1.0

Na 0.9

K 0.8

Rb 0.8

Cs 0.7

Fr 0.7

Ionization Energy

First Ionization EnergyIncreases UP and to the RIGHT

1

2

3

4 5

6

7

1

2

3

4 5

6

7

Melting/Boiling Point Highest in the middle of a period.

Melting/Boiling Point

Which atom has the larger radius?

Be or Ba

Ca or Br

Ba

Ca

Examples

Which atom has the higher melting/boiling point?

Li or C

Cr or Kr

C

Cr

Examples

Which particle has the larger radius?

S or S2-

Al or Al3+

S2-

Al

Examples