Chemistry - Covalent Bonding

What is a covalent bond formed between?

Atoms by sharing a pair of electrons

What is a covalent bond?

The electrostatic attraction between a shared pair of electrons and a positive nucleus

What groups form what bonds?

• Group 4 = 4 bonds

• Group 5 = 3 bonds

• Group 6 = 2 bonds

• Group 7 = 1 bond

• Hydrogen = 1 bond

Properties of simple covalent molecular structures

Have strong covalent bonds that DO NOT BREAK and between the molecules are weak intermolecular forces which are broken. They have low melting and boiling points because they ONLY break these weak intermolecular forces so little energy is requires to break them and allow the molecules to move apart

The larger the covalent molecules, the…

Higher the melting point, because larger molecules have stronger intermolecular attractions

Properties of giant covalent structures.

Solid at room temperature. They have high melting and boiling points because we have to break many strong covalent bonds which requires lots of energy.

Properties of Diamond

Each carbon has 4 bonds to other carbons in a tetrahedral arrangement. High melting point and hardness because it has many strong bonds which require lots of energy to break. Doesn’t conduct electricity because it has no charged particles to flow.

Properties of Graphite

Each carbon forms 3 bonds to other carbons. Hexagonal layers that can slide over each other. Melting point is high because strong covalent bonds must be broken to sperate atoms so require a lot of energy. Low hardness because each carbon is joined to 3 others in a layered structure and between layers are only weak intermolecular forces which slide over each other. It can conduct electricity because only 3 of carbon’s outer electrons are held in bonds. The 4th is delocalised and can carry charge through the structure.

Properties of Fullerene

Each carbon forms 3 bonds to other carbons. Balls and tubes. Simple molecular. C₆₀. Low melting point and low hardness because only weak intermolecular forces are broken. Can conduct electricity but on a nanoscale

Can covalent bonds conduct electricity?

Not usually because they have no charged particles to flow (no delocalised electrons or ions)