How atomic and ionic radii vary down the group?

Answer 1

Cations are most often metals, as cations are positively charged ions meaning they have lostelectron(s). As a general rule, metals are on the left-hand side of the Periodic Table. Since cations tend to lose electrons, their atomic radius will decrease in size, as the other electrons will be "pulled in" more by the protons in the nucleus (meaning stronger bond). This results in the atomic radius decreasing.

Anions on the other hand are most often nonmetals, as anions are negatively charged ions meaning they have gained electron(s). As a general rule, nonmetals are on the right-hand side of the periodic table. Since anions tend to gain electrons, their atomic radius will increase in size, as the newly added electrons will "shield" the other electrons from the nucleus, meaning they will be less attracted to the protons in the nucleus (meaning weaker bond). This results in the atomic radius increasing.

Note that the above trends mentioned apply mostly to the Group A elements. Many of the transition elements for covalent bonds, meaning they share electrons with other atoms, rather than giving or taking electrons from other atoms. However, many transition metals actually form cations, although there are some exceptions.

Answer 2

An ionic radius for an element is almost always smaller than the atomic radius. This is simple for cations, as the ionic radius must be lower because the highest occupied electron orbital becomes empty, making the outermost electron orbital the one below it. For instance, Sodium (+1) loses an electron from its 3S orbital, making the furthest occupied orbital the 2P. However, in the case for anions, like Chlorine (-1), the atom gains an electron, which would make sense to enlarge the atom. However, when an octet is formed, the electron orbitals become more stable and actually reduce the overall radius.

Answer 3

Idk.Trying to find that out myself.