Question

When two or more atoms of different elements combine in a definite proportion by mass, a ---------------------- is formed.

Answer 1

Molecule: Atoms of different elements combine in a definite proportion by mass, and a molecule of a compound is formed.

Example: Carbon reacts with Oxygen to form Carbon dioxide.

$\underset{\mathrm{Carbon}}{\mathrm{C}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{\mathrm{Dioxide}}{\underset{\mathrm{Carbon}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)}}$

Therefore when two or more atoms of different elements combine in a definite proportion by mass, a molecule of a compound is formed