Covalent bondingIB MYP Sciences: Mind map

Exam questions on Covalent bonding

1. Chlorine gas, Cl₂, is added to the water in public swimming pools in Singapore to kill bacteria. A chlorine atom has seven electrons in its outer shell, and a molecule of chlorine contains two chlorine atoms joined by a covalent bond.
   Describe, in terms of outer electrons, how the covalent bond forms between two chlorine atoms.2 marks
2. A fertiliser factory in Gujarat makes ammonia, NH₃, from nitrogen and hydrogen. A nitrogen atom has five electrons in its outer shell and a hydrogen atom has one. Ammonia is a gas at room temperature.
   Explain why ammonia has a low boiling point and does not conduct electricity.2 marks
3. A student in Nairobi compares two forms of carbon, diamond and graphite. She tries to scratch a glass slide with a sample of each. The diamond scratches the glass. The graphite does not scratch the glass and instead leaves a grey mark on it. She also finds that graphite conducts electricity but diamond does not, and both have very high melting points.
   Explain why graphite conducts electricity but diamond does not.3 marks