Bonds

Ionic bonding

[!def] metal atoms react with non-metal atoms

• Metal atoms lose, non-metal atoms gain their outer electrons to form ions
• The positive and negative ions are held together by strong electrostatic forces of attraction between opposite charges

Ionic bond

[!def] The force of attraction hold ionic compounds together

Examples

$$Na^+ + Cl^- \to NaCl$$
$$Mg^{2+} + O^{2-} \to MgO$$

Lattice structure

• Ionic compounds have a giant lattice structure (no molecule because it has no units)
• the atoms are arranged in an ordered and repeating fashion
  

Properties

• They have high melting and boiling points
• The greater the charge on the ions, the stronger the electrostatic forces and the higher the melting point will be

• good conductors of electricity in the molten state or in solution
• poor conductors in the **solid state

Covalent Bonding

[!def] pairs of electrons are shared between atoms

• Only non-metal elements participate in covalent bonding
• each atom gains a full outer shell of electrons
• Covalently bonded substances may consist of small molecules or giant molecules
• When two or more atoms are covalently bonded together, we describe them as ‘molecules’

Examples

$H_{2}O$
$CH_{4}$
$NH_{2}$
$H_{2} \ O_{2} \ Cl_{2}$ - single bond

Metallic bonding

[!def] the strong force of attraction between the positive metal ions and the delocalised electrons

• Metals consist of giant structures
• Within the metal lattice, the atoms lose their outer electrons and become positively charged metal ions
  • The outer electrons no longer belong to any specific metal atom and are said to be delocalised
  • This means they can move freely between the positive metal ions and act like a “sea of electrons”
    

Properties

- high melting and boiling points 
- strong electrostatic forces of attraction which needs lots of energy to be broken

• Metals are good conductors of heat and electricity
  • The delocalised electrons are free to move and carry a charge through the whole structure
• Most metals are malleable(opposite. brittle)
  • This means they can be hammered into shape
  • This is because the atoms are arranged in layers which can slide over each when force is applied