Important points
Groups ( 1 & 2 ) belong to the s-block of the Periodic Table .
Group 1 consists of : lithium , sodium , potassium , rubidium , caesium and francium and collectively known as the alkali metals .
Group 2 include : beryllium , magnesium , calcium , strontium , barium and radium . Except Beryllium they are known as alkaline
Physical properties-
a ) Large atomic radii : The atomic radii of alkali metals are the largest in their respective periods . These increase as we travel down the group .
b ) Large ionic radii : The ionic radii increase as we move down the group due to the addition of a new energy shell with each succeeding element .
c ) Low ionization enthalpy : The ionization enthalpies decrease as we move down the group . The ionization enthalpies of the alkali metals are the lowest due to loosely held s- electron .
d ) Hydration enthalpy : It decreases with the increase in ionic radii . The hydration enthalpy of Li ion is the maximum and the hydration enthalpy of Cs ion is the minimum .
e ) Oxidation state : The alkali metals exhibit oxidation state of + 1 in their compounds and are strongly electropositive in character . The electropositive character increases from Li to Cs .