Ionic Bonding

Ionic Bonding• Involves the transfer of valence electrons• Attraction between a cation and an anion• Cation

– Positively charged ion– Typically metals– But could be a polyatomic ion

• Anion– Negatively charged ion– Typically nonmetals– But could be a polyatomic ion

Ionic Bonding

Ionic Bonding

The oppositely charged ions are attracted to each other by a

force called an ionic bond

• Most ionic compounds:• Have high melting points• Are hard and brittle• Are soluble in water• Form electrolytes (conduct

electricity) when dissolved in water

Properties of Ionic Compound

Crystal Lattice Structure

• Ionic compounds form crystal lattices

• This explains why they have high melting points and are hard but brittle

Na+ Cl-

Ionic Compounds in Water

When ionic compounds dissolve, they separate into their ions

The free ions can now move and conduct electricity

Representing Ionic CompoundsLewis Diagrams

• Formation of sodium chloride:

Na + Na+ [ ]Cl

Cl

Lewis Structures for Ionic Compounds

Ba•

• O•••

•••

••O••

••

••Ba

2+ 2-

Mg•

•

Cl•••

••

••Cl•••

••••

••Cl••

••

••Mg

2+ -2

Ba and O

Mg and Cl

BaO

MgCl2

Representing Ionic Compounds

Criss-Cross MethodFor monatomic ions: Take the absolute value of the ionic charge for the cation and make it the subscript for the anion and vice versa.

Example: Al3+ and Cl-

The 3 becomes the subscript for the chloride ion and the 1 becomes understood for aluminum. Forming aluminum chloride: AlCl3

Representing Ionic Compounds

Criss-Cross MethodFor polyatomic ions: Additional step of including brackets around the polyatomic ion if it has a subscript other than one.

Example: Mg2+ and OH- The 2 becomes the subscript for the hydroxide ion, but brackets are needed to indicate 2 of each the O and the H. The 1 becomes the understood subscript for Mg. Forming magnesium hydroxide: Mg(OH)2

Polyatomic IonsNICK the CAMEL ate a CLAM for SUPPER in PHOENIX

• Underlined letter represents the symbol of the element.• The consonants represent the number of oxygen• The vowels represent the negative charge.

Eg. Underlined letter= NNumber of consanants= 3 represents

oxygensNumber of vowels= 1 represents charge

NO3- Nitrate