Molecules and Atoms

Molecules are two or more atoms bond together. It’s a smallest piece of substance. For example, CO2 (carbon dioxide) is composed by one carbon atom and two oxygen atoms. H2O (water) is composed by two hydrogen atoms and one oxygen atom. A single molecule of caffeine contains 24 atoms total: C8H10N4O2, 8 Carbon, 10 Hydrogen, 4 Nitrogen, and 2 Oxygen.

Each atom contains number of protons, neutrons, and electrons. For example, one oxygen atom has atomic structure of 8 protons, 8 neutrons, and 8 electrons. A hydrogen atom is the simplest chemical structure in the world. It contains 1 proton, 1 electron, and 0 neutron.