Question

Arrange the following cations in order of decreasing size :Ra2+,Sr2+,Ca2+,Ba2+.Also explain it.

Answer 1

Size increases as you go down the periodic table and increases as you go from right to left on the table.
https://en.wikipedia.org/wiki/Periodic_trends#/media/File:Periodic_trends.svg

Answer 2

As we know that on moving downwards in a group size decreases in periodic table.Therefore the order of decreasing size of the cations is :
Ra2+>Ba2+>Sr2+>Ca2+.

Answer 3

Thanks