Generally, when going down a group on the periodic table: atomic radii decrease ionic radii increase electronegativity increases reactivity decreases

Generally when we move down the group on a periodic table the atomic radii increases as the valency electrons occupy higher levels due to the increasing quantum number. Hence the atomic radii increases down the group.

The ionic radii increases down the group because while we move down the group the elements gain electrons and form ions called anions as an additional electron occupies the orbital the ions get bigger in size. Hence the ionic radii increase.

Electronegativity is described as the ability to attract and bind with electrons and it is a qualitative property. It decreases as we move down the group because the distance between the valency electrons and the nucleus increases. Hence electronegativity decreases down the group.

Reactivity increases as we move down the group as the metals have the tendency to lose electron form its outer shell.

Therefore the answer is ionic radii increases.

why do the isotopes of a particular element behave differently in nuclear reactions but the same in chemical reactions? chemical reactions involve changes to electrons in an atom; isotopes do not differ in electrons, and so they react the same way during chemical changes.