IB HL chemistry: 2.1 - metallic bonding and alloys

properties of metals

• Lustre (shiny appearance)

• Sonority (sound when struck)

• Malleability (can be reshaped on compression)

• Ductility (can be drawn out into a wire)

• Electrical conductivity

• Thermal conductivity

why is metal malleable

the unidirectional metallic bond lattice can shift in response to stress

why is metal thermally conductive

when in contact with heat, the delocalised electrons’ kinetic energy increases. the high kinetic energy electrons travel to a low heat energy area and so transfers heat energy

strength of metallic bond factors

• cation radius: the smaller the radius, the stronger the bond

• ionic charge: the greater, the stronger the bond as both the charge of the cation and the nmbr of delocalised electrons will be higher

  in combination those factors determine electron density

alloys

they are homogenous mixtures containing at least one metal and held together by metallic bonding

why does steel have a higher tensile strength than iron

• the carbon atoms inside the iron distorts the regular lattice

• stops the layers from easily sliding over each other when you apply force

component metals in stainless steel

• iron

• chromium

• carbon

popular because it doesn’t rust

nicrome

nickel and chromium

why are allows more correctly defined as mixtures rather than compounds

• allows don’t have a fixed composition

• could be separated using physical properties such as boilling point