Chemistry can often be placed at the center of a complex web showing the relationship between chemistry and many other pure and applied sciences. Atoms and Molecules Atoms are the building blocks of matter for chemists. They cannot be destroyed by chemical reactions but the reactions change the way the atoms are combined. Atoms are not the smallest particles of matter but they are composed of three types of smaller particles. These are the protons , electrons and neutrons .
Protons are a positively charged mass that is present in the nucleus which is the core of the atom.
Electrons are negatively charged particles that orbit the nucleus. The charge on an electron is equal to the charge on a proton. Neutrons are uncharged particles that, like protons, are present in the nucleus and have a mass slightly heavier than the proton. Protons and neutrons are held together by a strong nuclear forceFigure 2 is a simplified version of the carbon atom. It is composed of six protons, six neutrons and six electrons.