Which of the following increases in magnitude as the atomic number of alkali metals increases?

Options

A. Electronegativity
B. First ionisation potential
C. Ionic radius
D. Melting point

Answer

C

Explanation

Down the group, the atomic size increases with increasing atomic number and so attraction for shared pair of electrons decrease. Hence electronegativity decreases.
`(b)` Down the groups, the atomic size increases with increasing atomic number and so attraction between valence electron and nucleus decreases. Hence ionization energy decreases.
`(c)` Down the group atomic size increases with increase in number of atomic shells while effective nuclear charge remains constant.
`(d)` Down the group atomic size increases with increase in number of atomic shells and therefore, the strength of metallic bond decreases. So melting point decreases.