The elements in which the last electron enters the outermost s-orbital are called s-block elements. s-block has two groups (1 and 2).
- Group 1 elements are called alkali metals. They form hydroxides by reacting with water that is strongly alkaline in nature and hence are regarded as alkali metals.
- Whereas Group 2 elements are called alkaline earth metals. The oxides and hydroxides of these metals are alkaline in nature and exist in earth crust and hence are regarded as alkaline earth metals.