# Ionic Bonding¶

## Compounds¶

• A compound is a pure substance that contains two or more elements that are chemically bonded to each other
• Can be molecules or ions

## Types of bonds¶

#### Ionic¶

• Electrons are transferred from one atom to another and the resulting ions are held together with electrostatic forces
• Typically made from a metal and non-metal
• Are commonly identified as having an electronegativity difference ($$\Delta\chi$$) of $$>2$$
• The transfer of electrons is physical as the electrons move from the HOMO of one atom to the LUMO of another

#### Covalent¶

• The atoms do not take electrons, but instead the electrons sit between the atoms and are shared

#### Metallic¶

• The electrons delocalise and move freely between the interspersed metal atoms

## Ionic Compounds¶

• Compounds made from metal and non-metal elements are typically ionic
• The groups that they’re in can tell the resulting formula, e.g. $$\ce{CaBr2}$$ Calcium is in 2A and needs to get rid of two electrons. Bromine is in group 7A and needs to gain two electrons
• Polyatomic ions in a compound makes it an ionic compound, e.g. $$\ce{Ba(NO3)2}$$

• The nitrate component is a the nitrate ion $$\ce{NO3−}$$
• The $$\Delta\chi>2$$ rule is not quite accurate, as bonding character is not a cutoff, but instead can vary from strongly covalent to strongly ionic