State what is meant by the term covalent bond.
Describe or draw a dot-and-cross diagram to show the bonding in a molecule of nitrogen, N2\text{N}_2N2. Show only the outer shell electrons.
Substances A and B are covalently bonded and have simple molecular structures. The table below gives the boiling points for substances A and B.
| Substance | Boiling point in ∘C^\circ\text{C}∘C |
|---|---|
| A | -104 |
| B | -48 |
Explain why substances with simple molecular structures have low boiling points.
Suggest why the boiling point of B is higher than the boiling point of A.
Substance B has the empirical formula CH2\text{CH}_2CH2 and a relative molecular mass (MrM_rMr) of 42. Determine the molecular formula of substance B.
Substance X is also covalently bonded, but its structure is different from that of A and B. It has a boiling point of 3265 ∘C3265\ ^\circ\text{C}3265 ∘C.
Explain, in terms of its structure and bonding, why X has such a high boiling point.
15 exam-style questions on Edexcel IGCSE Chemistry Covalent bonding. Each one has a worked solution and a mark scheme showing where the marks go.