Here's why:

* Compound: A substance formed when two or more different elements are chemically combined in a fixed ratio.

* Mixture: A combination of two or more substances where each substance retains its own properties.

Table salt (sodium chloride, NaCl) is formed by the chemical bonding of sodium (Na) and chlorine (Cl) in a 1:1 ratio. These elements lose their individual properties and form a new substance with its own unique characteristics. You can't easily separate sodium and chlorine back out from table salt.