Answer:
An element is a pure substance that cannot be broken down into simpler substances by chemical means. Elements are made up of only one type of atom. For example, oxygen and hydrogen are elements.
A compound is a substance made up of two or more different elements chemically bonded together in a fixed ratio. The elements in a compound are held together by chemical bonds. For example, water (H2O) is a compound made up of hydrogen and oxygen atoms.
A molecule is a group of two or more atoms held together by chemical bonds. Molecules can be made up of atoms from the same element or different elements. For example, oxygen gas (O2) is a molecule made up of two oxygen atoms bonded together.
In summary, an element is a pure substance made up of only one type of atom, a compound is a substance made up of two or more different elements chemically bonded together, and a molecule is a group of atoms held together by chemical bonds.