Covalent bonding

Question 1

Covalent bonding happens between

Answer 1

Two or more non-metals

Question 2

How does covalent bonding occur

Answer 2

In compounds of non-metals

with a shared pair of electrons

Question 3

Are covalent bond strong or weak

Answer 3

VERY STRONG!!

Question 4

Explain covalent bonds in terms of electrostatic attractions

Answer 4

Strong bonds between atoms that are covalently bonded are the result of electrostatic attraction between the positive nuclei of the atoms and the pairs of
negative electrons that are shared between them

Question 5

Explain why substances with simple molecular structures are gases or liquids, or solids with low melting and boiling points

Answer 5

● Substances that consist of small molecules have WEAK INTERMOLECULAR FORCES between the molecules. These are broken in boiling or melting, not the covalent
bonds.

Question 6

Explain why the melting and boiling points of substances with simple molecular structures increase, in general, with increasing relative molecular mass

Answer 6

The intermolecular forces increase with the size of the molecules, so larger molecules (i.e. molecules with greater relative molecular masses) have higher melting and boiling points.

Question 7

Explain why substances with giant covalent structures are solids with high melting and boiling points

Answer 7

● Substances that consist of giant covalent structures are solids with very high melting points.
● All the atoms in these structures are linked to other atoms by strong covalent bonds.
● These bonds must be overcome to melt or boil these substances.

Question 8

Explain how the structures of diamond influence their physical properties, including electrical conductivity and hardness

Answer 8

• In diamond each carbon is joined to 4 other carbons
  covalently. So has many strong covalent bonds
• it’s very hard, has a very high melting point and does not conduct electricity.

Question 9

Explain physical structure of graphite including:

• Hardness
• Conductivity
• Melting/boiling point

Answer 9

• In graphite, each carbon is covalently bonded to 3 other carbons, forming layers of hexagonal rings, which have VERY WEAK forces of attraction between the layers, however strong covalent bonds between the molecules.
• The layers can slide over each other due to no covalent bonds between the layers, but weak intermolecular forces. Meaning that graphite is soft and slippery.
• One electron from each carbon atom is delocalised.
• This makes graphite similar to metals, because of its delocalised electrons.
• It can conduct electricity – unlike Diamond.

High melting/boiling points because they have strong covalent bonds between the atoms (NOT LAYERS) that require large amounts of energy to be overcome

Question 10

Covalent compounds do not usually conduct electricity except… explain why

Answer 10

• In graphite (delocalised electron which is free to move)

- In simple covalent molecules there are no charged particles therefore they cannot move

Question 11

Why doesn’t diamond conduct electricity

Answer 11

Because there are no charged particles free to move as each carbon is covalently bonded to 4 other carbons

Question 12

What shape is graphite arranged into

Answer 12

Hexagonal layers

Question 13

Describe the structure of silica or silicon dioxide

Answer 13

• Each oxygen is covalently bonded to 2 silicon atoms and each silicon atom is covalently bonded to 4 oxygen atoms
• there are twice as many oxygen atoms as silicon atoms