Question

Which of the following has highest atomic radius?

• A. ${\mathrm{Br}}^{-}$
• B. ${\mathrm{Cl}}^{-}$
• C. ${\mathrm{I}}^{-}$
• D. ${\mathrm{F}}^{-}$

Answer 1

The correct option is C

${\mathrm{I}}^{-}$

Explanation for the correct option:

(c ) ${\mathrm{I}}^{-}$

• Because the number of protons and neutrons increases down a group, thus the size of the nucleus grows-
• Furthermore, with each period, more energy levels are added. As a result, the orbital is larger, and hence the atomic radius is larger.
• ${\mathrm{I}}^{-}$ has largest radius.
• ${\mathrm{F}}^{-}<{\mathrm{Cl}}^{-}<{\mathrm{Br}}^{-}<{\mathrm{I}}^{-}$
• Hence this option is correct

Explanation for the incorrect options:

(a) ${\mathrm{Br}}^{-}$

• Because the number of protons and neutrons increases down a group
• ${\mathrm{F}}^{-}<{\mathrm{Cl}}^{-}<{\mathrm{Br}}^{-}<{\mathrm{I}}^{-}$
• ${\mathrm{Br}}^{-}$has less radius than that of ${\mathrm{I}}^{-}$.
• Thus, this option is incorrect.

(b) ${\mathrm{Cl}}^{-}$

• Because the number of protons and neutrons increases down a group
• ${\mathrm{F}}^{-}<{\mathrm{Cl}}^{-}<{\mathrm{Br}}^{-}<{\mathrm{I}}^{-}$
• ${\mathrm{Cl}}^{-}$has less radius than that of ${\mathrm{I}}^{-}$ and ${\mathrm{Br}}^{-}$
• Thus, this option is incorrect.

(d) ${\mathrm{F}}^{-}$

• Because the number of protons and neutrons increases down a group
• ${\mathrm{F}}^{-}<{\mathrm{Cl}}^{-}<{\mathrm{Br}}^{-}<{\mathrm{I}}^{-}$
• ${\mathrm{F}}^{-}$has less radius than that of ${\mathrm{I}}^{-}$. ${\mathrm{Br}}^{-}$and ${\mathrm{Cl}}^{-}$
• Thus, this option is incorrect.

Hence the correct option is (c ) ${\mathrm{I}}^{-}$