1.6 Covalent Bonding

Question 1

Covalent bond formation

Answer 1

A covalent bond is formed when a pair of electrons is shared between two atoms

Question 2

Covalent bonds

Answer 2

Covalent bonds are strong and form between non-metal atoms and often produce molecules, which can be elements or compounds.

A hydrogen atom can form one covalent bond. Usually, for atoms of other non-metals:
- number of bonds = (8 - group number)

For example, in group 4, carbon can form 4 covalent bonds
In group 5, nitrogen can form 3 covalent bonds because 8 - 5 = 3
In group 6, oxygen can form 2 covalent bonds because 8 - 6 = 2
In group 7, chlorine can form 1 covalent bond because 8 - 7 = 1
In group 8, helium cannot form any covalent bonds because it has a full outer shell.

Question 3

Dot and cross diagrams

Answer 3

There are three ways you can represent a covalent bond:
1] dot-and-cross (with shells)
2] dot-and-cross (without shells)
3] structural formula
H-H

When you draw diagrams like these: draw overlapping circles to represent the outer shells

Draw a dot to represent an electron from one atom, and a cross to represent an electron from the other atom (make sure each bonding pair of electrons is between the two atoms)

Make sure that each atom (apart from hydrogen) has eight electrons in its outer shell

Question 4

Examples of covalent bonds

Answer 4

Hydrogen chloride, H-Cl
Water, H-O-H
Methane, C-H-H-H-H
Oxygen, O-O
Carbon dioxide, O=C=O