Question

the diagram is an illustration of a common substance found in the atmosphere. is the substance an atom or a molecule? oa it is an atom because it has a nucleus. ob it is an atom because c and o are subatomic particles. oc it is a molecule because it is held together by energy and not chemical bonds. od it is a molecule because it has two different elements that are held together by bonds.

Explanation:

An atom is the smallest unit of an element, while a molecule is made up of two or more atoms held together by chemical bonds. The diagram shows a combination of carbon (C) and oxygen (O) atoms forming a substance, which is carbon - dioxide ($CO_2$). It is a molecule because it consists of different elements (carbon and oxygen) bonded together.

Answer:

D. It is a molecule because it has two different elements that are held together by bonds.