Past Paper Questions

Question 1

State and explain the trend in electronegativities across Period 3 from sodium to sulfur.

Answer 1

Electronegativity increases
Proton number increases (increase in nuclear charge)

Same number of electron shells/levels

Attraction of bond pair to nucleus increases

Question 2

Explain why the oxides of the Period 3 elements sodium and phosphorus have different melting points. In your answer you should discuss the structure of and bonding in these oxides, and the link between electronegativity and the type of bonding.

Answer 2

Big difference in electronegativity leads to ionic bonding, smaller covalent
Sodium oxide ionic lattice
Strong forces of attraction between ions
P4O10 covalent molecular
Weak (intermolecular) forces between molecules
melting point Na2O greater than for P4O10

Question 3

Explain why the bond enthalpy of a Cl–Cl bond is greater than that of a Br–Br bond.

Answer 3

Bond is shorter or bonding pair closer to nucleus
So attraction (between nucleus and) (to) bond pair is stronger