JEE Main · 2026 · 04 Apr 2026 · Shift 1 · Classification of Elements and Periodicity

A monoatomic anion

(A X^{-})

has 45 neutrons and 36 electrons. Atomic mass, group in the periodic table and physical state at room temperature of the element (A) respectively are:

(A)80, 17, liquid✓ Correct
(B)81, 16, solid
(C)80, 16, gas
(D)81, 15, gas

Answer: (A)

Solution

The anion

A X^{-}

has 36 electrons, so neutral A has 35 electrons and hence 35 protons, i.e.

Z = 35

, which is bromine. Its mass number is protons plus neutrons,

35 + 45 = 80

. Bromine lies in group 17 and exists as

Br X_{2}

, a liquid at room temperature. Thus the atomic mass is 80, the group is 17 and the physical state is liquid.

JEE Main · 2026 · 04 Apr 2026 · Shift 1 · Single correct option

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