Section 3: Periodic Trends

Electronic

Structure

of Atoms

Ato

mic

Ra

diu

sin

cre

as

es

Periodic TrendsAtomic Radius decreases

Can you explain in terms of

nuclear charge & shielding

Electronic

Structure

of Atoms

Ato

mic

Ra

diu

sin

cre

as

es

Periodic TrendsAtomic Radius decreases

Ele

ctro

neg

ativ

ity?

??

Ionization Energy ???

Electronegativity ???

Ion

iza

tion

En

erg

y?

??

Electronic

Structure

of Atoms

Ionization Energy (IE):•energy required to

remove an e–

Down a Group:decreases ↓

Across a Period:increases ↑WHY?

+

Electronic

Structure

of Atoms

decre

ases

do

wn

a g

rou

p

First IE Trends

-due to

more

shielding

(less

attraction)

increases across a period

-due to greater nuclear charge

(more attraction)

+

Example of Ionization Energy Trend

• Arrange the following elements in order of

increasing first ionization energy.

Mg, Na, Si, Al

Electronic

Structure

of Atoms

Electronegativity (EN) Trends • atom’s ability to attract bonded e–’s

decre

ase

sd

ow

n a

gro

up

increases across a period

-due to

more

shielding

(less

attraction)

-due to greater nuclear charge

(more attraction)

Example of Electronegativity Trend

• Arrange the following elements in order of

increasing electronegativity: B, Na, F, O

Overall Reactivity – Very Important!

• The most reactive metals are the

largest since they are the best

electron givers.

• The most reactive nonmetals are

the smallest ones since they are

the best electron takers.

Overall Reactivity

0

Electronic

Structure

of Atoms

Ato

mic

Ra

diu

sin

cre

as

es

Periodic Trends (Summary)Atomic Radius decreases E

lectro

neg

ativ

ityd

ec

rea

se

sIonization Energy increases

Electronegativity increases

Ion

iza

tion

En

erg

yd

ec

rea

ses

Can you explain all of this

in terms of p’s and e’s?

nuclear charge

shielding

Electronic

Structure

of Atoms

Ato

mic

Ra

diu

sin

cre

as

es

Periodic Trends (Summary)Atomic Radius decreases E

lectro

neg

ativ

ityd

ec

rea

se

sIonization Energy increases

Electronegativity increases

Ion

iza

tion

En

erg

yd

ec

rea

ses

Can you explain all of this

in terms of p’s and e’s?

nuclear charge

shielding