SUMMARY

The elements of groups 1 and 2 of the modern periodic table are called s-block elements, since their differentiating electron occupies an s orbital. Group 1's general outer configuration is ns¹ -- the alkali metals; group 2's is ns² -- the alkaline earth metals, so called because they occur in the earth's crust and their oxides/hydroxides are alkaline.

Both families are highly reactive, forming M⁺ and M²⁺ cations respectively, and both show a regular trend down their group: atomic and ionic radii increase, while ionisation enthalpies decrease.

The first member of each group -- lithium in group 1, beryllium in group 2 -- differs noticeably from the rest of its own family and instead resembles the second member of the next group (magnesium, aluminium respectively). This pattern is called the diagonal relationship.

The alkali metals are soft, silvery-white, low-melting and highly reactive; their compounds are predominantly ionic. They form metal hydrides and halides with hydrogen and the halogens respectively, and their oxides/hydroxides dissolve in water to form strong alkalies. Sodium's important compounds -- sodium carbonate, sodium chloride, sodium hydroxide and sodium bicarbonate -- are made industrially by the Solvay process and the Castner-Kellner process respectively. …