3.1.2/3.1.3/3.1.4 Group 2, the halogens and qualitative analysis GapFill

The elements in group 2 are called the alkaline earth metals, while those in group 7 (17) are known as the  halogenschromogenschalcogenspnictogens. Their highest-energy electrons lie in  s and ds and pd and sp and s subshells, respectively.

The chemistry of the group 2 elements is dominated by  2+3-3+1+ ions; these are formed more readily further down the group, mainly because of lower first and second  ionisationneutralisationcombustionformation energies. Group 2 hydroxides are often used as bases, as in the treatment of  fludiabetesindigestionheadaches with Mg(OH)₂.

In their elemental forms, the group 7 (17) elements exist as X₂ molecules, with boiling points increasing further down the group due to stronger  ionic bondingLondon dispersion forcespermanent dipole-dipole interactionshydrogen bonding. Their chemistry is characterised by   4-3-2-1- ions and simple covalent compounds. That said, they sometimes take part in reactions where they are oxidised, as well as reduced; these are called  biproportionationexproportionationdisproportionationcomproportionation reactions. The presence of group 7 (17) anions in solution is tested for using an acidified solution of  copperplatinumsilvergold nitrate.