Topic 2 - COVALENT Bonding (III)

Question 1

What is a COVALENT BOND?

Answer 1

Formed between two NON-METAL atoms by SHARING A PAIR OF ELECTRONS in order to fill their outer shell.

Question 2

What is COVALENT BONDING?

Answer 2

A strong attraction shared between a pair of electrons and two nuclei.

Question 3

Explain the difference between simple molecular structure and intermolecular forces within a molecule.

Answer 3

Within each molecule there are atoms bonded to each other COVALENTLY.
These covalent bonds inside the molecules are strong.
But between the molecules are weak forces of attraction that require little energy to break. (not covalent forces)

This is why simple molecular substances such as CO2 have a low boiling point.
When the substances change from one state to another (e.g: solid to gas), covalent bonds within each molecule remain unbroken.
Instead, it is the weak forces of attraction between each molecule that break.

Question 4

Why do the melting and boiling points of substances with simple molecular structures increase, in general, with increasing relative molecular mass?

Answer 4

Larger molecules tend to have higher melting points.

• because larger molecules (with more mass) have more forces of attraction between them.
• these forces, although weak, must overcome if substance boils + larger molecules have more attractions which must be overcomed.

Question 5

Why do substances with giant covalent structures are solids with high melting and boiling points?

Answer 5

Giant covalent structure with many strong covalent bonds that require a lot of energy to break.

Question 6

Structure of DIAMOND

Answer 6

• made from carbon atoms only
  very hard (giant covalent with many strong covalent bonds)
• DOESNT CONDUCT ELECTRICITY
• high melting + boiling point
• each atom covalently bonded to 4 OTHERS

Question 7

Structure of GRAPHITE

Answer 7

• made from carbon atoms only
• soft + slippery (weak forces of attraction between layers)
• CONDUCTS ELECTRICITY
• high melting + boiling point
• each atom covalently bonded to 3 OTHERS

Question 8

Structure of FULLERINE (C60)

Answer 8

• made of carbon atoms only
• soft (weak intermolecular forces of attraction between molecules)
• DOESNT CONDUCT ELECTRICITY
• low melting + boiling point (only intermolecular forces are broken)
• each atom covalently bonded to 3 OTHERS