structure and bonding

Question 1

ionic bonding

Answer 1

metal and non metal. the particles are oppositely charged. held by electrostatic forces of attraction. gaining or losing electrons.

Question 2

covalent bonding

Answer 2

non-metal atoms. sharing pairs electrons

Question 3

metallic bonding

Answer 3

metal atoms and alloys. atoms share delocalised electrons

Question 4

what is an ionic compound

Answer 4

a giant structure of ions.
- held together by strong electrostatic forces of attraction between oppositely charged ions

Question 5

limitations of dot and cross diagram

Answer 5

useful for showing how ionic compounds are arranged but do not show structure, size or how it is arranged

Question 6

limitations of ball and stick model

Answer 6

shows the regular pattern of an ionic crystal and shows how the ions are arranged. it shows that it also extends beyond the diagram
- however is not to scale, so the relative sizes of the ions may not be shown, also there arent actually gaps between ions

Question 7

why are covalently bonded atoms strong?

Answer 7

positively charged nuclei is attracted to the electrons of the shared electrons by electrostatic forces.

Question 8

why is methane a gas at room temperature

Answer 8

it is a small molecule so it has weak intermolecular forces which require little energy to overcome

Question 9

why can metals conduct electricity

Answer 9

they have metallic bonding so
- electrons in outershell of metal atoms are delocalised and so free to move through structure
- sharing of delocalised electrons gives rise to strong metallic bonds

Question 10

limitations of simple particle model

Answer 10

in the model there are no forces, that all particles are represented as spheres and that the spheres are solid

Question 11

properties of ionic compounds

Answer 11

• regular structures where there are strong electrostatic forces of attraction in all directions between oppositley charged ions
• high melting and boiling points as large amount of energy to break stromg bonds
• when melted or dissolved in water, they conduct electricity as ions are free to move and charge can flow

Question 12

properties of small molecules

Answer 12

• gases or liquids that have relativley low melting and boiling points
• weak intermolecular forces between molecules that are easily overcome
• intermolecular forces increase with size of molecules, so larger molecules have higher melting and boiling points
• these substances do not conduct electricity becaue the molecules do not have an overall electric charge

Question 13

what are polymers

Answer 13

very large molecules
- atoms in polymer are linked to other atoms by strong covalent bonds.
- intermolecular forces between polymer molecules are strong so they are solids at room temperature

Question 14

what are giant covalent structures

Answer 14

solids with very high melting points
- all the atoms in the structures are linked to other atoms by string covalent bonds. these bonds must be overcome to melt or boil the substances
- eg: diamond, graphite, silicon dioxide

Question 15

structure of pure metals

Answer 15

atoms are arranged in layers so they can be bent and shaped. they are too soft for many uses and so are mixed with other metals to make alloys which are harder

Question 16

why are alloys harder than pure metals

Answer 16

different elements have different sized atoms. so when another element is mixed with a pure metal, the new metal atoms will distort the layers of metal atoms, making it more difficult for them to slide over each other, which makes them harder than pure metals.

Question 17

why are metals good conductors of electricity

Answer 17

• the delocalised electrons in metals carry charge though the metal.
• also good thermal energy conductor because energy is transferred by delocalised electrons

Question 18

structure and properties of diamons

Answer 18

• each carbon atom forms 4 covalent bonds with other carbon atoms in a giant covalent structure
• makes it hard, high melting point and does not conduct electricity

Question 19

graphite - structure, bonding and properties

Answer 19

• each carbon atom forms 3 covalent bonds with other carbon atoms leaving one electron from each atom to be delocalised which means it can conduct electricity and thermal energy
• it forms layers of hexaginal rings which have no covalent bonds between the layers. this means they can move over each other so graphite is soft and slippery - so used as a luricant

Question 20

what is graphene

Answer 20

a single layer of graphite.
- covalent bonds make it strong, but also lightweight
- delocalised electrons make it useful in electronics

Question 21

what are fullerenes

Answer 21

• molecules of carbon atoms with hollow shapes
• hexagonal rings of carbon atoms but also contain rings with 5 or 7 carbon atoms
• buckministerullerenes are spherical in shape

Question 22

uses of fullerenes

Answer 22

• used to deliver drugs around the body
• large surface area so could be useful catalysts
• as lubricants

Question 23

what are carbon nanotubes

Answer 23

cylindrical fullerenes with high length to diameter ratios
- can conduct electricity and thermal energy
- have a high tensile strength
- used in nanotechnology, electronics, and materials

Question 24

nanoparticles - properties

Answer 24

• high surface area to volume ratio which means tjat it has properties differet from those for the same materials in bulk. means smaller quantities are needed to be effective

Question 25

nanoparticles - uses

Answer 25

• catalysts as sa to v ratio is huge
• some conduct electricity
• silver nanoparticles have antibacterial properties so could be added to polymer fibres for surgical masks, dressings, deodrants
• in suncreams and cosmetics