Question

An atom has $2K,8L$ and $5M$ electrons.
Choose the correct statement(s) regarding it.
A. Trivalent anion of this atom will have $12$ protons in its nucleus.
B. Trivalent cation of this atom will have six p-electrons in it.
C. This atom form an amphoteric oxide of formula $X_2{O}_3$.
D. One of its allotrope is tetra atomic $\left(X_4\right)$

• A. $B$ and $C$
• B. $B$ and $D$
• C. $A$ and $B$
• D. $B$ only

Answer 1

Answer: (B)

In given atom the structure is, K(2) L(8) M(5)

Configuration will be:

$X=1s^{2}2s^{2}2p^{6}3s^{2}3p^3$

$X–3e\to X^{3+}$

So, it will be trivalent metal cation.

$X^{3+}=1s^{2}2s^{2}2p^{6}3s^2$

So, p electrons will be 6.

As per the configuration, this element is the phosphorous (atomic number 15). It exists as allotrope in tetra atomic i.e. $X_4$ format.

The correct option is D.