The s-block element is made up of two series: Group 1 Elements and Group 2 Elements.
Elements of group-1 are called alkali metals and those of group-2 are called alkaline earth metals. Group-1 elements are called alkali metals as these metals form oxides and hydroxides which combine with water to form alkali. Alkali word is derived from the Arabic word ‘alquis’ meaning plant ashes which are rich in the carbonates of sodium and potassium. Group-1 consists of the following elements Hydrogen (Z=1), Lithium (Z=3), Sodium (Z=11), Potassium (Z=19), Rubidium (Z=37), Caesium (Z=55), Francium (Z=87).
Hydrogen is placed in the first period, lithium in the second period, sodium in the third period, potassium in the fourth period, rubidium in the fifth period, caesium in the sixth period and francium in the seventh period.
Atomic numbers of noble gases are, He, Ne, Ar, Kr, Xe, Rn are 2, 10, 18, 36, 54, 86 respectively.
In group 1, each of these elements, the last electron (differentiating electron) enters the ns orbital of the atom. The general electronic configuration of the group element is ns^1. All alkali metals have one valence electron hence forming monovalent M^+ ions and are highly reactive. Alkali metals do not occur in nature in the free state.
Read more about Group 13 Elements, here.
The elements belonging to group 2 are called alkaline earth metals as these metals form alkaline oxides and hydroxides and these metal oxides occur in the earth’s crust.
Hydrogen is placed in the first period, beryllium in the second period, magnesium in the third period, calcium in the fourth period, strontium in the fifth period, barium in the sixth period and radium in the seventh period. Group 2 consists of the following elements Beryllium (Z=24), Magnesium (Z=212), Calcium (Z=20), Strontium (Z=238), Barium (Z=56), Radium (Z=88).
Atomic numbers of noble gases are, He, Ne, Ar, Kr, Xe, Rn are 2, 10, 18, 36, 54, 86 respectively.
In group 2, each of these elements, the last electron (differentiating electron) that enters the ns orbital of the atom. The general electronic configuration of the outermost shell
of group-2 elements is ns^2.
All alkaline earth metals have two valence electrons, hence form divalent M2+ ions, and are highly reactive. Like alkali metals, even alkaline earth metals do not occur in nature in a free state.
Learn more about Group 14 Elements, here.