A compound is composed of at least two atoms. Each atom must be a different element. An element is composed of at least one atom. Atoms from the same element are identical. An atom is composed of at least three particles. Most atoms also have neutrons and electrons.
Explanation:
Matter is composed of small units called atoms so we can say that atom are the building blocks of matter. Atom is composed of three particles i. e. proton, neutron and electron. Proton and neutron are present in the nucleus while electron revolve in the orbits. Element is a pure substance which is made of similar atoms while compounds are made of more than one atom which combines with each other in a fix ratio by mass.
