C3

Question 1

non-metallic elements form

Answer 1

simple molecules with covalent bonds between atoms

Question 2

covalent substances are formed when?

Answer 2

when atoms of non-metals combine.

Question 3

describe the formation of single covalent bonds

Answer 3

they are the sharing of pairs of electrons leading to the noble gases configuration (see dot and cross diagrams - the ones that overlap on pg 49)

Question 4

Describe the differences in volatility between ionic and covalent compounds.

Answer 4

Covalent compounds have low melting and boiling points.
Ionic bounds have high boiling and melting points.

Covalent compounds are more volatile.

(volatile = evaporates easily)

Question 5

Describe the differences in solubility between ionic and covalent compounds.

Answer 5

ionic compounds are usually soluble in water
covalent compounds are less soluble.

Question 6

Describe the differences in electrical conductivity between ionic and covalent compounds.

Answer 6

Ionic compounds can conduct electricity when melted or dissovled, and the lattice breaks up and ions are free to move.

Covalent compounds are not charged, thus they do not conduct electricity.

Question 7

know how to draw the diagrams for more complex covalent molecules

Answer 7

pg 51

Question 8

what kind of intermolecular forces do ions and simple covalent compounds have (why are ions’ melting and boiling points higher?)

Answer 8

ions have strong intermolecular forces (so high melting and boiling points)
simple covalent has weak intermolecular forces (so low melting and boiling points)

• they have different attractive forces. ions’ are harder to break

Question 9

what are allotropes

Answer 9

they are different forms of the same element

Question 10

what are allotropes

Answer 10

they are different forms of the same element

Question 11

there are many different forms of _____

Answer 11

carbon. including diamond and graphite.

Question 12

describe the giant covalent structures of graphite and diamond.

Answer 12

diamond: each carbon atom is joined to four other carbon atoms by strong covalent bonds. the carbon atoms form a regular network structure. there are no free electrons

graphite: each carbon atom forms three covalent bonds with other carbon atoms. the carbon atoms form layers of hexagonal rings. there are no covalent bonds between the layers. there is one non-bonded - or delocalised - electron from each atom

Question 13

how do the structures of diamond and graphite relate to their uses?

Answer 13

all the covalent bonding in diamond is very strong which makes an extremely hard substance. it’s why diamonds are used in cutting.

graphite also has strong covalent bonds, but they have weak forces of attraction (weak IMFs). so, the layers slide over each other which makes It a good lubricant. it can also conduct electricity.

Question 14

describe the macromolecular structure of silicon oxide

Answer 14

every silicon atom has four covalent bonds, it is similar to diamond which is why silicon oxide is hard and has a high melting point.