Covalent Bonding- T3

Question 1

What is a covalent bond?

Answer 1

A strong bond consisting of a shared pair of electrons.

Question 2

What is a dative covalent bond?

Answer 2

A covalent bond where both electrons are donated from one of the atoms, shown by an arrow.

Question 3

Why do simple covalent structures have low melting and boiling points?

Answer 3

Due to weak intermolecular forces between molecules.

Question 4

What are giant covalent structures made up of?

Answer 4

Non metals covalently bonded together in a 3D structure.

Question 5

3 examples of macromolecules/ giant covalent structures:

Answer 5

Diamond, Graphite and SiO2 (sand)

Question 6

What are the properties of Diamond and why?

Answer 6

1) Hard (4 bonds to each C). 2) High melting points (strong covalent bonds). 3) Doesn’t conduct electricity (no delocalised electrons).

Question 7

3 properties of graphite: (and why)

Answer 7

1) Soft and slippery (layers can slide over each other). 2) High melting point (strong covalent bonds). 3) Conducts electricity and heat (has delocalised electrons).

Question 8

2 examples of simple covalent structures:

Answer 8

Carbon dioxide and water.

Question 9

Why does melting point increase from Na — Al?
(Period 3)

Answer 9

Delocalised electrons increase, so stronger metallic bonds. Ionic radius decreases, charge on atom increases.

Question 10

Why is melting point the highest at Si?
(Period 3- Silicon)

Answer 10

It is a macromolecular structure with strong covalent bonds.

Question 11

Why does melting point from P to Ar decrease?

Answer 11

Larger molecules have stronger intermolecular forces. (P4, S8, Cl2 and Ar)- weaker intermolecular forces.