Chemists use the number of outer shell electrons in atoms to predict the bonding in molecules they have not seen before.
The table shows the number of outer shell electrons in atoms of some elements.
| Element | Number of electrons in outer shell |
|---|---|
| hydrogen | 1 |
| carbon | 4 |
| nitrogen | 5 |
| phosphorus | 5 |
| oxygen | 6 |
| chlorine | 7 |
Ammonia has the formula NH3\mathrm{NH_{3}}NH3. Determine the number of bonding pairs and the number of non-bonding pairs of electrons in the outer shell of the nitrogen atom in ammonia.
Phosphorus trichloride has the formula PCl3\mathrm{PCl_{3}}PCl3. Each chlorine atom forms one covalent bond with the phosphorus atom.
Determine the total number of non-bonding pairs of electrons in one molecule of phosphorus trichloride.
In a molecule of hydrogen cyanide, HCN, the carbon atom is bonded to both the hydrogen atom and the nitrogen atom.
Explain, in terms of outer shell electrons, why there is a triple bond between the carbon atom and the nitrogen atom.
In hydrogen peroxide, H2O2\mathrm{H_{2}O_{2}}H2O2, the two oxygen atoms are joined to each other and each oxygen atom is joined to one hydrogen atom. All the bonds are single bonds.
Give the total number of covalent bonds in a molecule of hydrogen peroxide.
53 exam-style questions on Edexcel GCSE Chemistry 2.4 Covalent bonding, covering 2.4.1 Covalent bonding and simple molecules. Each one has a worked solution and a mark scheme showing where the marks go.