The modern periodic table has been divided into blocks based on the presence of valence electrons in the s, p, d or f orbital. They are divided into s-block, p-block, d-block and f-block. s-block elements of the periodic table are elements in which the electrons enter the s-orbital. s-orbital has the capability of holding only 1 or 2 electrons in its outermost orbital. Depending upon the number of electrons present in the outer orbital, they are classified as Group 1 or Group 2 elements. General electronic configuration of Group 1 and Group 2 elements are ns1 and ns2
Elements of the Group 1 are:
Elements of Group 2 are:
Alkali metal is the collective name given to Group -1 elements and alkali earth metal is the name given to Group-2 elements. Elements of group-1 are given the name alkali metals due to the formation of hydroxides when they react with water. Alkali earth metals are so called due to the formation of oxides and hydroxides which are alkaline and also, earth’s crust mainly consists of these metal oxides.
Sodium and potassium are widely available while the alkali metals such as rubidium and cesium are less abundant in nature. Francium is a radioactive element which has a half-life of only 21 minutes. Among the alkali earth metals, calcium and magnesium are widely available in the earth’s crust whereas barium and strontium are less abundant in nature. Availability of beryllium and radium is very rare.
First elements of Group 1 and Group 2 i.e. lithium and beryllium exhibit few properties which are different from other elements in the group. It is observed that elements of group 1 exhibit similar properties to the second element of the successive group. This type of similarities is referred to as the diagonal relationship in the modern periodic table. This might be due to the similarities in ionic size or radius ratio of the two successive elements. Ions of the s-block elements are responsible for performing important biological functions. To familiarize yourself with this topic better, it would be ideal if you could solve certain solved questions and answers like the NCERT Solutions for S Block Elements.