Which of the following statements about a compound is incorrect ?
(a) A molecule of a compound has atoms of different elements
(b) A compound cannot be separated into its constituent elements by physical methods of separation
(c) A compound retains the physical properties of its constituent elements
(d) The ratio of atoms of different elements in a compound is fixed
A ___________ is a substance made up of two or more elements.
Different allotropic forms of an element have different chemical properties but same physical properties.