Question
Describe metallic bonding and how it contributes to electrical conductivity. [3]
Answer/Explanation
Ans
electrostatic attraction between «a lattice of» cations/positive «metal» ions AND «a sea of» delocalized electrons mobile electrons responsible for conductivity OR
electrons move when a voltage/potential difference/electric field is applied
Do not accept “nuclei” for “cations/positive ions” in M2. Accept “mobile/free” for “delocalized” electrons in M2. Accept “electrons move when connected to a cell/battery/power supply” OR “electrons move when connected in a circuit” for M3.
Question
Copper is a metal that has been used by humans for thousands of years.
State the full electron configuration of \(^{{\text{65}}}{\text{Cu}}\).[1]
State one difference in the physical properties of the isotopes \(^{{\text{63}}}{\text{Cu}}\) and \(^{{\text{65}}}{\text{Cu}}\) and explain why their chemical properties are the same.
Physical:
Chemical:[2]
Describe the bonding in solid copper.[2]
Answer/Explanation
Markscheme
\({\text{1}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{s}}^{\text{2}}}{\text{3}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{d}}^{{\text{10}}}}{\text{4}}{{\text{s}}^{\text{1}}}{\text{/1}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{s}}^{\text{2}}}{\text{2}}{{\text{p}}^{\text{6}}}{\text{3}}{{\text{s}}^{\text{2}}}{\text{3}}{{\text{p}}^{\text{6}}}{\text{4}}{{\text{s}}^{{\text{13}}}}{{\text{d}}^{{\text{10}}}}\);
Physical:
\(^{{\text{63}}}{\text{Cu}}\) lower boiling point/melting point/density/greater rate of diffusion than \(^{{\text{65}}}{\text{Cu}}\);
Accept converse argument.
Do not accept “different mass”.
Chemical:
(properties identical because) same electron configuration/arrangement of electrons;
Accept “same number of protons and electrons”.
Do not accept “same number of electrons” OR “same valence (electrons)” OR “same atomic number” only.
electrostatic attraction;
between (a lattice of) cations/positive ions and delocalized/sea of electrons;
Do not award any mark for only stating “metallic bonding”.
Examiners report
Most were able to quote the electron configuration of copper correctly; but some gave [Ar] \({\text{4}}{{\text{s}}^{\text{1}}}\,{\text{3}}{{\text{d}}^{\text{9}}}\) when they were specifically asked for the full configuration. A few, inevitably gave \({\text{3}}{{\text{d}}^{\text{9}}}\,{\text{4}}{{\text{s}}^{\text{2}}}\). In (b), few related the difference in mass to a property and most did not give the comparison; “the same number of electrons and protons” was more popular than “the same electron configuration”. The descriptions of metallic bonding were disappointing; the mark for electrostatic attraction was rarely scored and many confused “nuclei” with “cations/positive ions”.