The first ionisation energies of elements show periodic trends across periods and groups in the periodic table.
Using the first ionisation energy of lithium, Li\text{Li}Li, as 520 kJ mol−1520\text{ kJ mol}^{-1}520 kJ mol−1, calculate the energy required to form one Li+(g)\text{Li}^+(\text{g})Li+(g) ion from one Li(g)\text{Li}(\text{g})Li(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 helium, He\text{He}He, and beryllium, Be\text{Be}Be, are both higher than the first ionisation energy of lithium, Li\text{Li}Li.
Explain why the first ionisation energy of beryllium, Be\text{Be}Be, is higher than that of boron, B\text{B}B.
