Simple molecules and covalent bonds：练习题

Which statement correctly describes a covalent bond?

Which statement accurately describes the bonding and properties of a simple molecular compound like carbon dioxide, $$CO_2$$?

Which of the following correctly describes the distribution of electrons in one molecule of nitrogen, \( \text{N}_2 \)?

Which statement correctly describes the covalent bonding in a molecule of methane, \( CH_4 \)?

In a molecule of ammonia, \(NH_3\), how many lone pairs of electrons are present on the nitrogen atom?

State how many electrons are shared in a single covalent bond and describe the goal of atoms when they form such bonds.

Explain why a molecule of nitrogen, \( \text{N}_2 \), contains a triple covalent bond and requires a high amount of energy to break.

Contrast the boiling points of water, \( \text{H}_2\text{O} \), and methane, \( \text{CH}_4 \), by referring to the types of forces that must be overcome during boiling.

Nitrogen gas, \(\text{N}_2\), is a simple molecular substance.
a) Draw a dot-and-cross diagram to show the bonding in a nitrogen molecule. Show only the outer shell electrons.
b) Nitrogen gas is very unreactive. Explain this property by referring to the bonding within the molecule.
c) Explain why nitrogen has a very low boiling point in terms of its structure and the forces between molecules.

Carbon dioxide, \(CO_2\), and silicon(IV) oxide, \(SiO_2\), are both oxides of Group IV elements, yet they have very different physical properties.
a) Describe the bonding in a molecule of carbon dioxide, referring to the number of shared electron pairs.
b) Explain, in terms of structure and bonding, why carbon dioxide is a gas at room temperature while silicon(IV) oxide is a solid with a very high melting point.