identify each item as either an element or a compound. carbon (c) carbon dioxide (co₂) hydrogen (h) sodium…

Brief Explanations:

An element is a pure substance made of only one kind of atom. A compound is a substance made up of two or more different elements chemically combined. Carbon (C) and hydrogen (H) are made of only one - type of atom, so they are elements. Carbon dioxide ($CO_2$) is made of carbon and oxygen atoms, and sodium chloride ($NaCl$) is made of sodium and chlorine atoms, so they are compounds.

Answer:

carbon (C): element carbon dioxide ($CO_2$): compound hydrogen (H): element sodium chloride ($NaCl$): compound