Covalent Bonding Recap

Oxygen has a low boiling point because there are...

• weak covalent bonds between the oxygen atoms

• weak covalent bonds between the oxygen molecules

• weak forces of attraction between the oxygen atoms

• weak forces of attraction between the oxygen molecules

Which pair of elements combine together to form a covalent molecule?

• aluminium and oxygen

• carbon and sulfur

• lithium and nitrogen

• magnesium and sulfur

Draw the dot and cross diagram for CS₂

Answer explanation

C likes to form 4 bonds, which each S likes to form 2. So C will form 2 doubles bonds with the S (1 double bond each).

In which molecule are there no lone pairs on any of the atoms?

• HF

• H₂O

• NH₃

• CH₄

Substance X melts at 118^oC and boils at 299^oC. Predict its structure and bonding

• Giant Ionic

• Giant Covalent

• Simple Covalent

• Metallic

Substance X melts at 118^oC and boils at 299^oC. Predict its (a) solubility in water and (b) electrical conductivity.

Draw one line from each statement to the diagram which shows the structure.

Answer explanation

Which property is common to both diamond and graphite?

• Each atom in the structure forms four covalent bonds

• They are suitable to use as a lubricant

• They are electrical insulators

• They have high melting points

A substance has a high melting point. When solid, it does not conduct electricity but when molten it does conduct. Which type of structure and bonding does the substance have?

• giant ionic

• metallic

• simple molecular

• giant covalent

The melting point of aluminium oxide is much higher than the melting point of calcium oxide. Which statement explains this?

• A calcium ion has more protons than an aluminium ion

• A calcium ion has more shells of electrons than an aluminium ion

• A calcium ion has a smaller charge than an aluminium ion

• Calcium is more reactive than aluminium