The s-bloxk elements of the Periodic Table are those in which the last electron enters the outermost s-orbital. As the s -orbital can accommodate only two electrons, two groups(1&2) belong to the s-block of the Periodic Table. Group 1 of the periodic table consists of the elements: lithium, sodium, potassium, rubidium, caesium and francium. They are collectively known as alkali metals. These are so called because they form hydroxides on reaction with water which are strongly alkaline in nature.

The elements of group 2 include beryllium, magnesium, calcium, strontium, barium and radium. These elements with the exception of beryllium are commonly known as alkaline earth metals. These are so called because their oxides and hydroxides are alkaline in nature and these metal oxides are found in earth's crust. Strontium and barium have much lower abundances. Beryllium is rare and radium is the rarest of all comprising onpy 10-10 % of igneous rocks.

The general electronic configuration of s-block elements is [noble gas]ns1-2.