JEE Main · 2023 · 10 Apr 2023 · Shift 1 · s-Block Elements

The compound which does not exist is

(A) $NaO_{2}$ ✓ Correct
(B) $(NH_{4})_{2} BeF_{4}$
(C) $BeH_{2}$
(D) $PbEt_{4}$

Answer: (A)

Solution

Among the choices, ammonium tetrafluoroberyllate, beryllium hydride and tetraethyllead are all well-characterised, stable compounds. The remaining species is written as a sodium superoxide. Sodium is a small cation that cannot stabilise the large, singly charged superoxide ion; with oxygen it forms the peroxide

Na_{2} O_{2}

, while stable superoxides of the form

MO_{2}

are given only by the larger alkali metals potassium, rubidium and caesium. The species that does not exist under ordinary conditions is sodium superoxide.

JEE Main · 2023 · 10 Apr 2023 · Shift 1 · Single correct option

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