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.