Crystal types

Question 1

name the five types of structure

Answer 1

• monatomic
• simple molecular
• ionic
  -giant covalent
• metallic

Question 2

what are the melting and boiling points like of ionic structures? why?

Answer 2

very high - large amount of energy needed to overcome the strong electrostatic forces of attraction between oppositely charged ions

Question 3

what is the electrical conductivity like in ionic structures? why?

Answer 3

conduct electricity when molten or in an aqueous solution (not when solid) - ions free to move when molten or dissolved so can move to the electodes

Question 4

what is the strength like of ionic structures?

Answer 4

very brittle - dislocation leads to the layers moving and similar ions being adjacent. the repulsions splits the crystal

Question 5

what is the solubility like of ionic structures?

Answer 5

insoluble in non-polar solvents but soluble in water - water is a polar solvent and stabilises the separated ions. partial charges of water pull oppositely charged ions apart and break apart the ionic lattice

Question 6

what are the melting and boiling points like of metallic structures? why?

Answer 6

high - string electrostatic attraction between ions and delocalised electrons

Question 7

what is the electrical conductivity like of metallic structures?

Answer 7

conductive - delocalised outer shell electrons free to move and carry a charge

Question 8

what is the strength of metallic structures?

Answer 8

strong - layers can slide while maintaining metallic bonding due to delocalised electrons

Question 9

are metallic structures soluble? why?

Answer 9

insoluble - metallic bonds too strong

Question 10

what giant covalent structures conduct electricity? why?

Answer 10

graphite and graphene - coordination number = 3 - one delocalised electron per carbon atom free to move and carry charge

Question 11

what are the melting and boiling points like of giant covalent structures? why?

Answer 11

very high - many covalent bonds to be broken- large amount of energy needed

Question 12

what is the strength of giant covalent structures? exception?

Answer 12

strong and hard except graphite - soft due to weak van der Waals’ forces between layers.

Question 13

what is diamond so hard?

Answer 13

exist in rigid tetrahedral structure

Question 14

solubility of giant covalent structures?

Answer 14

insoluble

Question 15

what are the melting and boiling points like of simple molecular structures?

Answer 15

low- weak intermolecular forces

Question 16

how do the MP and BP change as the size of molecules change? why?

Answer 16

as surface area of molecules increase, the MP and BP increase - intermolecular forces get stronger

Question 17

electrical conductivity of simple molecular structures?

Answer 17

insulators - no mobile electrons

Question 18

strength of simple molecular structures?

Answer 18

brittle - weak intermolecular forces

Question 19

solubility of simple molecular substances?

Answer 19

tend to be more soluble in organic solvents than in water; some are hydrolysed (broken down by water)

Question 20

density of ice vs water explanation

Answer 20

ice is less dense than water - in ice, molecules are arranges in lattice due to H-bonds; as a liquid molecules are closer as not in a lattice