Question

Particles are arranged in a crystal structure in a sample of
(1) H2(g) (3) Ar(g)
(2) Br2(l) (4) Ag(s)

Answer 1

the answer is (4) Ag(s)

Solid Silver has a Face Centered Cubic crystal structure.

The remaining choices are gases (H2 & Ar) and liquid (Br). Liquids and gases do not form crystal structures as their atoms are loose.