let's learn the difference between an atom a molecule and a compound welcome to moomoomath and science the smallest unit of matter is called an atom each atom is made up of smaller particles known as subatomic particles in the nucleus or the middle of an atom are two subatomic particles called the proton and the neutron the positively charged particles in the nucleus of an atom are called protons the number of protons in the nucleus is the defining property of an element and is referred to as the atomic number the uncharged particles in the nucleus are called neutrons orbiting the nucleus of an atom is a cloud of negatively charged particles called electrons the electrons are much smaller in mass than the protons and neutrons the mass of an atom is based on the sum of the mass of the protons and the neutrons a molecule is when you take individual atoms and physically connect them together the atoms are stuck together by either sharing the electrons which is a covalent bond a molecule like ozone can be two or more of the same atom another example is when you stick two hydrogen atoms to one oxygen atom you get water in addition you have compounds a compound occurs when you combine elements together chemically but for it to be a compound these elements must be different an element is a pure substance consisting of only atoms that have the same number of protons chemical elements cannot be broken down into simpler substances by chemical means you can find all the elements on the periodic table of the chemical elements an example of a compound would be sugar this occurs when you take carbon hydrogen and oxygen and you get sugar thanks for watching and remember kindness multiplies kindness be kind to someone today you