Question

1. what is a compound?

examples:
elements that are chemically combined

Explanation:

A compound is a substance made of two or more different elements that are chemically combined in a fixed ratio. Examples include water ($H_2O$, hydrogen and oxygen), carbon dioxide ($CO_2$, carbon and oxygen), and sodium chloride ($NaCl$, sodium and chlorine).

Answer:

A compound is a substance formed from two or more different elements that are chemically combined in a fixed proportion. Examples: Water ($H_2O$), Carbon Dioxide ($CO_2$), Sodium Chloride ($NaCl$)