Properties of Covalent compound

(a) Low melting points and boiling points

Because:

-          Molecules held by weak intermolecular forces.

-          Needs less energy to overcome these forces.

-         

(b) Cannot Conduct electricity

Because:

-          consists of neutral molecules.

-          Do not have ions that can move freely.

(c) does not dissolve in water

(d) dissolve in organic solvents.

Properties of Ionic compound

(a) High melting points and boiling points.

Because:

-          Ions held by strong electrostatic forces.

-          Needs a lot of energy to overcome these forces.

(b) Conduct electricity when in molten or aqueous solution.

Because:

-          In solid, ions are fixed in positions and do not move freely.

-          In molten state or aqueous solution, the ions can move freely.

(c) dissolve in water

(d) does not dissolve in organic solvents.

Covalent Bond (non-metal + non-metal) Sharing of electron

[proton number: C:6, O:8]

- Electron arrangement of atom C is 2.4

- Atom C needs 4 more electron to achieve stable octet electron arrangement.

- Atom C contributes 4 electron for sharing

- Electron arrangement of atom O is 2.6

- Atom O needs 2 more electron to achieve stable octet electron arrangement

- Atom O contributes 2 electron for sharing.

- covalent compound, CO₂ is formed

Ionic Bond (metal + non metal) Transfer of electron

[number of proton: Mg: 12, O: 8]

- Electron arrangement of magnesium atom is 2.8.2

- Magnesium atom donates 2 electron to achieve stable octet electron arrangement.

  Mg → Mg²⁺ + 2e

- Electron arrangement of oxygen atom is 2.6

- Oxygen atom receives 2 electron to achieve stable octet electron arrangement.

   O + 2e → O^2-

- Mg²⁺ ion and O^2‑ ion attract by strong electrostatic force to form ionic bond.

- Ionic compound, MgO is formed.