Answer:
i. Atomic radius of an atom is defined as the total distance from the nucleus to the outermost shell of the atom.
On moving from left to right ( Mg, K) in a period, more and more electrons get added up in the same shell and the attraction between the last electron and nucleus increases, which results in the shrinkage of size of an atom. Thus, decreasing the atomic radii of the atom on moving towards right of the periodic table.
As moving from top to bottom, there is an addition of shell around the nucleus and the outermost shell gets far away from the nucleus and hence, the distance between the nucleus and outermost shell increases.
Thus the order of atomic radii is : Ca > Mg > K
ii. The energy required to remove the last valence electron from isolated gaseous atom (first ionization energy) increases as we move from left to right in a period. It decreases on moving from top to bottom.
Thus the order of first ionization energy is : K > Mg > Ca
iii. The chemical properties depend on the valence elctrons and as the elements Mg and Ca both have two valence electrons , they have same chemical properties.
