Question

Element with atomic number 38 belongs to

• A. $IIA$ group and $5^{th}$ period.
• B. $IIA$ group and $2^{nd}$ period.
• C. $VA$ group and $2^{nd}$ period.
• D. $IIIA$ group and $5^{th}$ period.

Answer 1

The correct option is A

$\mathrm{IIA}$ group and $5^{\mathrm{th}}$ period.

Part 1: Explanation for the correct answer:

Option A: $\mathrm{IIA}$ group and $5^{\mathrm{th}}$ period.

Electronic Configuration of the element with atomic number $38$

${}_{\mathbf{38}}\mathbf{X}\mathbf{}\mathbf{=}\mathbf{}\mathbf{2}\mathbf{,}\mathbf{8}\mathbf{,}\mathbf{18}\mathbf{,}\mathbf{8}\mathbf{,}\mathbf{2}$

1. To check the period of an element count the number of shells in the configuration.
2. To check the group we can check the number of electrons in the valence shell.

From the above configuration,

1. There is $5$ shell in which the electron is filled. So, the element belongs to $5\mathrm{th}$ period.
2. In the valence shell only $2$ electron are present. So, the element belongs to group $2$.

Part 2: Explanation for incorrect options:

Option B: $\mathrm{IIA}$ group and $2^{\mathrm{nd}}$ period.

1. To be a member of $2^{\mathrm{nd}}$ period, the element must have only $2$ shell. but the given configuration has $5$shell.

Option C: $\mathrm{VA}$ group and $2^{\mathrm{nd}}$ period.

1. To be a member of $2^{\mathrm{nd}}$ period, the element must have only $2$ shell. but the given configuration has $5$shell.
2. The valence electron should be $5$ to be a member of $\mathrm{VA}$ group.

Option D: $\mathrm{IIIA}$ group and $5^{\mathrm{th}}$ period.

1. The valence electron should be $3$ to be a member of $\mathrm{IIIA}$ group.

Hence, Option A is correct. Electronic Configuration of the element with atomic number $38$ is II A group and 5^th period.