Answer: Because of the arrangement of atoms in a compound.
Step-by-step explanation:
A compound is defined as the chemical specie which is formed by the combination of two or more different type of atoms. For Example:
etc...
A compound has different physical and chemical properties than corresponding elements because of change in identity. For Example: Hydrogen and oxygen are gases, but the compound formed by the combination of these two that is water is liquid.
In a chemical compound, elements are combined in a fixed ratio of their masses.
Hence, a compound has characteristic property because of the arrangement of atoms in a compound