The first ionisation energies of elements show periodic trends across periods and groups in the periodic table.
Using the first ionisation energy of sodium, Na\text{Na}Na, as 496 kJ mol−1496\text{ kJ mol}^{-1}496 kJ mol−1, calculate the energy required to form one Na+(g)\text{Na}^+(\text{g})Na+(g) ion from one Na(g)\text{Na}(\text{g})Na(g) atom. Give your answer in kJ\text{kJ}kJ, in standard form, and to two significant figures. (Avogadro constant, NA=6.02×1023 mol−1N_A = 6.02 \times 10^{23}\text{ mol}^{-1}NA=6.02×1023 mol−1)
Explain why the first ionisation energies of neon, Ne\text{Ne}Ne, and magnesium, Mg\text{Mg}Mg, are both higher than the first ionisation energy of sodium, Na\text{Na}Na.
Explain why the first ionisation energy of magnesium, Mg\text{Mg}Mg, is higher than that of aluminium, Al\text{Al}Al.
