The first and second ionization energies for two unknown elements are shown
CHEMISTRY · Single correct · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends
Problem
The first and second ionization energies for two unknown elements are shown.
Element X: IE₁ = 496 kJ mol⁻¹, IE₂ = 4560 kJ mol⁻¹
Element Y: IE₁ = 738 kJ mol⁻¹, IE₂ = 1450 kJ mol⁻¹
Both elements are in Period 3. Which statement best explains the large difference between the second ionization energies of X and Y?
(a) Element X has a higher effective nuclear charge than Element Y, so all of its electrons are held more tightly, producing the larger jump in IE₂.
(b) After losing one electron, Element Y already achieves a noble-gas configuration; consequently its second electron is removed from a more shielded shell and requires less energy.
(c) For Element X, removal of a second electron would have to break into the n=2 shell, which is much closer to the nucleus; therefore a far greater amount of energy is required.
(d) The second electron removed from Element Y comes from a 3p orbital that is higher in energy and more shielded than a 3s electron, so its IE₂ is comparatively low.