Chapter 15

Ionic Bonding

Valence Electrons

Do the electron configuration for the following elements

• Li• Be• B• O• F• Ne

Valence Electrons

• Now look at the outermost electrons by looking at the last s and p orbital

• Circle and count these electrons• These are the valence electrons

Valence electrons

– Valence electrons are in the highest energy level of an element’s atom

– Valence electrons are the same as group # (roman numeral) for the group A representative elements

– Valence electrons are usually the only electrons used in chemical bonds

– We use valence e- to write Lewis Dot Structures

Valence electrons (cont.)

A. Lewis Dot Structure Ex: bromine

Br● ●

●●●

● ●

Electron configurations for cations & anions

A. Octet Rule: when forming compounds atoms want to have 8 electrons (s2p6) like the noble gases (except He)

Na (atom)

1s22s22p63s1

●

lose 1 e-

Na (cation)

+1s22s22p6

octet

Using the Dot Structure

Na (neutral

atom)

Na (cation)

lose 1 e- +

●

Mg (neutral

atom)

Mg (cation)

lose 2 e-2+

●

Cations (metals) tend to lose electrons, positively charged ion

gain 2e-

Cl

(neutral atom)

O (neutral

atom)

Cl (atom)

1s22s22p63s23p5

●

gain 1 e-

Cl (chloride ion)

-1s22s22p63s23p6

octetUsing the Dot Structure

Cl

(chloride ion)

-

●

O

(oxide ion)

2-●

●●

●

● ●

● gain 1 e-

●

●●●

●

●●

●●

●

valence

● ●

●●●

● ●

●

●

●

Anions (Nonmetals) have negative charges because they gain electrons

Practice

N

I

Li

Ca

●

●

●

●

●

N

(nitride ion)

3-gain 3e-

●

●●

●●●

●

●

●

●

●

●

●

●●

I

(iodide ion)

gain 1 e-

●

●●

●●

●●

●

-

●

LiLose 1 e- +

CaLose 2e- +2

●

●

Ionic Compound

1. ionic compounds form crystals2. high melting and boiling points3. hard and brittle4. conduct electricity when dissolved in

water or melted

A. Properties

•Composed of a metal (cation) and nonmetal (anion)•Ionic bond – oppositely charged ions attract•Electrically neutral (+) = (-)

Ionic Bonds

Na Cl

1. Sodium and Chlorine

●● ●

●●

●

●

●

donates e-

Na+ ● Cl●

●●

●

●

●

●

2. Potassium and Oxygen

KO

●

●●

●

●●

donates e -

K+● O

●●●

●●

●

●●

+

+

K● donates e-

K+

-2

+1 -2

-

K2O

NaCl

+1 -1

Al

3. Aluminum and Bromine

Mg N●

●●

●●

Mg+2● N

●●●

●●

●

●●

+● Mg+2

-3

● ●●●

●●

●●

Al+3

● Br●

●●

●

●

●

●

+●

●

Br● ●

●●

●●

●Br

● ●●●

●●

●Br

+3 -1

● Br●

●●

●

●

●

●

● Br●

●●

●

●

●

●

-

-

-+2 -3

Mg

4. Magnesium and Nitrogen

Mg●

●

●

●

N●

●

●●

●

Mg+2● N

●●●

●●

●

● -3

AlBr3

Mg3N2

OUTPUT EXAMPLE:

1. Potassium & Fluorine

+1 -1

K●

F● ●

●●

●●+ ● K + F● ●

●●

●●●●

KF

-