Question

Which of the following ions is largest in size?

• A. ${Li}^{+}$
• B. ${Na}^{+}$
• C. $K^{+}$
• D. ${Ca}^{2+}$

Answer 1

Answer: (C)

$K^{+}$

While down the group atomic radius increases and left to right in period atomic radius decrease. Also when electrons are lose (Positive sign, making it cation) its atomic radius decrease because when electrons are lose there is more nuclear attraction on rest electrons and so it decreases the atomic radius hence size decreases.

Thus $K^{+},C{a}^{+2}$ have larger radius than other. But $K^{+}$ have greater radius because it loses only one electron. So its size is larger.