Paper 2 · June 2014 · Atomic Structure and Bonding
Fig. 1 shows the first ionisation energies of the elements sodium to argon. The value for aluminium is lower than that for magnesium because the electron removed from aluminium
Ais closer to the nucleus
Bcomes from a 3p orbital, which is higher in energy than the 3s
Ccomes from a completely filled 3s orbital
Dexperiences a greater nuclear charge
Explanation
The 3p electron of aluminium is slightly further from the nucleus and better shielded, so it is easier to remove.
Derived from ZIMSEC Chemistry Paper 2, June 2014, Q1