1g Covalent bonding

Question 1

Which type of elements form covalent compounds and why?

Answer 1

When 2 non metals form covalent bonds they both gain electrons to get a full outer shell

Question 2

How is a covalent compound formed?

Answer 2

When 2 non metals both gain electrons by sharing

Question 3

What is a covalent bond?

Answer 3

This is a result of a strong electromagnetic attraction between the bonding pair of electrons and the nuclei of atoms involved in the bond.

Question 4

What are the 3 giant covalent lattice structures?

Answer 4

diamond, graphite and silicon dioxide

Question 5

What are the properties of a simple molecular solid?

Answer 5

The weak forces of attraction between molecules in molecular solids only require a small amount of energy to be broken. This means that molecular solids:
- Have low melting and boiling points
- Are usually soft and brittle - they shatter when hit
- Are usually insoluble in water but soluble in other solvents such as petrol
- Cannot conduct electricity - there are not free electrons to carry an electrical charge

Question 6

What is an allotrope?

Answer 6

Different structure forms of the same element in the same physical state. They have the same chemical properties (as they have the same number of electrons) but different physical properties (as the electrons are shared in different ways with atoms).

Question 7

What are the properties of silicon dioxide?

Answer 7

• It has a high melting point because it is a giant covalent structure because it has giant covalent bonds which are very strong which require a lot of energy to break the bonds apart.
• It cannot conduct electricity because it doesn’t have any ions.
• It is very hard like diamond although it isn’t made of carbon

Question 8

What is the structure of silicon dioxide?

Answer 8

• sand is an impure form of silicon dioxide (quartz). It has a giant covalent structure with certain similarities to diamond
• Each silicon atom (2.8.4) is bonded to 4 oxygen atoms, and each oxygen atom (2.6) is bonded to two silicon atoms.

Question 9

What is the structure of graphite?

Answer 9

• Graphite is a common form of carbon in which each atom is covalently bonded together.
• This forms rings of 6 atoms, creating a giant structure containing many layers. These layers are held together by weak forces of attraction

Question 10

What are the properties of graphite?

Answer 10

• It has a high melting point because it is a giant covalent structure because it has giant covalent bonds which are very strong which require a lot of energy to break the bonds apart.
• It can conduct electricity because it has delocalised electrons that are able to move around.
• Graphite is soft because it has weak intermolecular forces of attraction between the molecules which can be easily broken

Question 11

What is the structure of diamond?

Answer 11

• Diamond is a rare form of carbon in which each atom is covalently bonded to 4 others.
• This pattern arrangement is repeated millions of times to create a giant lattice structure

Question 12

What are the properties of diamond?

Answer 12

• It has a high melting point because it is a giant covalent structure because it has giant covalent bonds which are very strong which require a lot of energy to break the bonds apart.
• It cannot conduct electricity because every carbon atom has 4 strong carbon atoms bonded together meaning it has no delocalised electrons
• Diamond is the hardest natural substance on earth

Question 13

What are the properties of simple molecular structures? (in detail)

Answer 13

• Low melting and boiling points because they have weak intermolecular forces of attraction between the molecules that can easily be broken
• They can’t conduct electricity because they have no charged electrons that are able to move around freely.
• They are soft because they have weak intermolecular forces of attraction between the molecules which can be broken very easily