Solid Lattices

Question 1

what are metallic lattices composed of

Answer 1

• a regular arrangement of positive metal ions

- surrounded by a sea of delocalised electrons

Question 2

what are giant ionic lattices composed of

Answer 2

a regular arrangement of positive and negative ions

Question 3

what are giant covalent lattices composed of

Answer 3

• a giant network of atoms

- linked to each other by covalent bonds

Question 4

how are the carbon atoms in diamond arranged

Answer 4

• each one has 4 sigma bonds to 4 other carbon atoms

- forming a giant 3-dimensional tetrahedral arrangement

Question 5

what are the bond angles between the carbon atoms in diamond

Answer 5

109.5

Question 6

why is diamond very hard and have a high melting temp

Answer 6

• the C-C bonding throughout the structure is very strong
• the number of strong C-C bonds that need to be broken in order to melt it require a lot of energy
• the tetrahedral arrangement also gives it geometrical strength (solid frame)

Question 7

what is the structure of each layer of graphite like

Answer 7

• each carbon atom is bonded to 3 others by sigma bonds

- forming interlocking hexagonal rings

Question 8

why does graphite have its layered structure

Answer 8

• the 4th electron in each carbon atom is in the p orbital
• the layers are close enough for the carbon atoms p orbitals to overlap with each other
• forming weak london forces between the layers to keep them together

Question 9

what makes graphite a good conductor of electricity

Answer 9

the overlapping of p orbitals forms a cloud of delocalised electrons above and below the plane of rings

Question 10

why can graphite be used as a solid lubricant

Answer 10

because its layers easily slide over each other

Question 11

why does graphite have this layer sliding property

Answer 11

• because of the absorbed gases on the surface of the carbon atoms
• not the fact that the london forces between the layers are weak

Question 12

why is graphite a good conductor of electricity

Answer 12

because the delocalised electrons are free to move under the influence of a potential difference

Question 13

what makes graphite special in terms of how it conducts electricity compared to metals

Answer 13

• because of its layered structure it can only conduct electricity parallel to its layers
• the electrons cant move between these layers
• whereas metals can conduct electricity in all directions

Question 14

what is graphene

Answer 14

one layer of graphite

Question 15

how is solid iodine formed

Answer 15

• the iodine molecules I2 arrange themselves in a regular pattern
• the diatomic molecules are bonded together by london forces

Question 16

what is the structure of solid iodine called

Answer 16

face-centered cubic (but its a molecular solid)

Question 17

why are the melting and boiling points of molecular solids low

Answer 17

• because you only need to overcome the intermolecular forces of attraction between the molecules to melt them
• usually being london forces, they are weak

Question 18

why does ethene have such a lower melting point than poly(ethene)

Answer 18

• poly(ethene) has many more electrons in a single molecule
• meaning that the number of london forces would increase
• they are also longer molecules
• allowing for more possible points of contact for london forces to form
• the overall increase in london forces is what gives poly(ethene) the higher melting temp