Question

Q: give reasons:

a) atomic size of pottasium is more than that of sodium?

Answer 1

To understand this fact let us have a look at the electronic configuration of both elements that is Sodium and Potassium.
Na : 2,8,1
K : 2,8,8,1
These elements belong to the group 1 of periodic table and we know as we down the group atomic size increases because moving down the shell increases and outermost electrons become farther from the nucleus. This increase distance between the outermost valence electrons and nucleus causes decrease in attracting power of nucleus . Thus ultimately it leads to increase in atomic size of an element as we move down the group in periodic table.