Question

Which of the following does not increase on moving down a group?

• A. Atomic radius
• B. Metallic character
• C. Valence Electrons
• D. Shells in atoms

Answer 1

The correct option is C

Valence Electrons

An explanation for the correct option

1. Electrons present in the last shell of an atom are termed valance electrons.
2. For any given group in the periodic table, valency remains the same and also valence electrons remain the same.

Let’s take an example of Group 1 i.e. alkali metals

$$\begin{gathered} {}_{3}Li=2,1 \\ {}_{11}Na=2,8,1 \\ {}_{19}K=2,8,8,1 \\ {}_{37}Rb=2,8,18,8,1 \\ {}_{55}Cs=2,8,18,18,8,1 \end{gathered}$$

An explanation for the incorrect option:

1. Atomic radius could be defined as the distance from the nucleus to the outermost shell or for any combined atom it is half the internuclear distance. And if we go down the group number of shells (n) increases and as a result atomic radius increases. Hence option (A) is incorrect.
2. When atomic radius increases, ionization potential decreases (amount of energy required to pull an electron from the outermost shell of an isolated gaseous atom), so ejecting electrons from the outermost shell becomes easy, and hence metallic character increases. So option (B) is incorrect.
3. As we go down shells in atoms increases. Hence option (D) is incorrect.

Option (C) is correct, and option (A), (B) and (D) are incorrect.