chemistry - key concepts in chemistry: types of substance (1.32 - 1.42)

1.32 ionic - structure, bonding, physical properties, solubility, conductivity

most compounds containing metal & non-metal atoms

ionic bonds - electrons lost & gained, oppositely charged ions attract each other

billions of ions held together in lattice structure

high melting/boiling points - strong bonds

many soluble in water

conduct electricity when molten/aqueous, not solid - charged particles can move

1.32 simple molecular (covalent) - structure, bonding, physical properties, solubility, conductivity

most non-metal elements & compounds

covalent bonds - pairs of electrons shared between atoms

small, distinct group of atoms

low melting/boiling points - weak intermolecular forces

few soluble in water

most don’t conduct electricity - no charged particles

1.32 giant covalent - structure, bonding, physical properties, solubility, conductivity

few non-metal elements, some non-metal compounds

covalent bonds - pairs of electrons shared between atoms

billions of atoms held together in lattice structure

high melting/boiling points - strong bonds

insoluble in water

most don’t conduct electricity (except carbon as graphite) - no charged particles

1.32 metallic - structure, bonding, physical properties, solubility, conductivity

found in all metals

metallic bonds - electrostatic attraction between +ve metal ions & -ve delocalised electrons

billions of +ve ions held together in giant lattice structure in ‘sea’ of -ve delocalised electrons

high melting/boiling points - strong bonds

insoluble in water

conduct electricity when solid/liquid - charged particles can move

1.33 ionic compounds - high melting/boiling points

strong electrostatic forces of attraction between oppositely charged ions

require lots of energy to overcome

1.33 ionic compounds - conduction of electricity in diff. states

charged ions carry current

don’t conduct when solid - ions cannot move

conduct when molten/aqueous - ions can move

1.34 covalent, simple molecular compounds - low melting/ boiling points

strong covalent bonds

weak intermolecular forces (must be overcome)

don’t require much energy to overcome

1.34 covalent, simple molecular compounds - poor conduction of electricity

electric current = flow of charged particles

strong forces between -ve electrons & +ve nuclei hold electrons in place

electrons cannot flow - cannot carry current

allotrope

different structural forms of same element

1.35 graphite & diamond - form & substance

different forms (allotropes) of carbon

giant covalent substances

1.36 graphite - structure

covalent, giant molecular

each carbon atom covalently bonded to 3 carbon atoms - layered structure, not all electrons in covalent bonds

weak forces of attraction between sheets of carbon atoms

1.36 diamond - structure

covalent, giant molecular

each carbon atom covalently bonded to 4 carbon atoms

1.37 graphite - electrodes

conducts electricity well - delocalised electrons can move & carry electrical current

cheap

not very reactive

1.37 graphite - lubricant

soft - weak forces of attraction between layers, can slide past each other

1.37 diamond - cutting tools

hard - rigid network of carbon atoms in tetrahedral arrangement, strong covalent bonds

1.38 C₆₀ - properties, structure & bonding

simple molecule

each carbon atom covalently bonded to 3 carbon atoms

ball shape

low melting points - weak intermolecular forces

soft & slippery - weak intermolecular forces

strong molecules - strong covalent bonds

1.38 graphene - properties, structure & bonding

sheet of carbon atoms (1 atom thick)

strong - strong covalent bonds

conducts electricity - delocalised electrons can move & carry current

1.39 simple polymers - e.g. poly(ethene)

large molecules

contain chains of covalently bonded carbon atoms

1.40 metals - malleable

layers of ions slide over each other

‘sea’ of electrons holds ions together

metal changes shape, doesn’t break

1.40 metals - good conduction of electricity

delocalised electrons move randomly in all directions between +ve metal ions

p.d. applied between 2 points on metal - electrons flow to +ve side

flow of electrons - transfers energy, forms electrical current

1.41 dot & cross diagrams - problems

don’t show structure formed

suggest electrons in diff. atoms are diff. - they’re the same

1.41 ball & stick models - problems

show atoms too far apart

not ‘sticks’ holding atoms together

1.41 2D representations - problems

don't show 3D arrangements of atoms

1.41 3D representations - problems

don’t show transfer of electrons

1.42 metals vs non-metals

metals: shiny solids, high melting points, high density, good conductors of electricity

non-metals: low boiling points, poor conductors of electricity