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