NEET 2018 · ChemistryPrevious Year Question

Magnesium reacts with an element $X$ to form an ionic compound. If the ground-state electronic configuration of $X$ is $1 s^{2} 2 s^{2} 2 p^{3}$ , the simplest formula for this compound is:

Answer: (D) $Mg X_{3} X X_{2}$ . \textbf{Answer:} (D) $Mg X_{3} X X_{2}$ \textbf{Solution:} The configuration $1 s^{2} 2 s^{2} 2 p^{3}$ has 5 valence electrons (group 15), so $X$ has a valency of 3 (gains 3 electrons to form $X X^{3 -}$ ).

A. $Mg X_{2} X$
B. $MgX X_{2}$
C. $Mg X_{2} X X_{3}$
D. $Mg X_{3} X X_{2}$ ✓

Correct Answer

(D) $Mg X_{3} X X_{2}$

Solution & Explanation

\textbf{Answer:} (D) $Mg X_{3} X X_{2}$ \textbf{Solution:} The configuration $1 s^{2} 2 s^{2} 2 p^{3}$ has 5 valence electrons (group 15), so $X$ has a valency of 3 (gains 3 electrons to form $X X^{3 -}$ ). Magnesium has a valency of 2 ( $Mg X^{2 +}$ ). Cross-combining the valencies gives the formula $Mg X_{3} X X_{2}$ .

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Magnesium reacts with an element X to form an ionic compound. If the ground-state electronic configuration of X is 1s22s22p3, the simplest formula for this compound is:

Solution & Explanation

More NEET PYQ solutions

Magnesium reacts with an element $X$ to form an ionic compound. If the ground-state electronic configuration of $X$ is $1 s^{2} 2 s^{2} 2 p^{3}$ , the simplest formula for this compound is: