Which of the following correctly describes a compound?

Option (a) is the correct statement.

Explanation:

A substance that has two or more number of different atoms which are chemically combined to each other in a fixed ratio by mass is known as a compound.

For example,

Here, contains one atom of calcium and two atoms of chlorine which are chemically combined together in 1:2 ratio. Therefore, it is a compound.

Also, both chemical and physical properties of will be different from Ca and .

Thus, we can conclude that the statement atoms are bonded together, and the compound has different physical and chemical properties than the individual element, is correct.