By Joan Whetzel | Updated Mar 24, 2022
Atoms consist of a nucleus of protons and neutrons, surrounded by a cloud of electrons. The positive charge of protons attracts the negatively charged electrons, keeping them bound in orbit.
Atomic mass approximates the mass of the nucleus, roughly 1,800 times that of an electron. It is calculated by adding protons and neutrons. For instance, a carbon atom has six protons and six neutrons, giving an atomic mass of 12.
The atomic number equals the number of protons in the nucleus. In a neutral atom, this also equals the number of electrons. Carbon’s atomic number is 6 because it contains six protons and six electrons.
While the proton’s positive charge attracts electrons, it can also lose electrons to other atoms. A neutral atom maintains balance when its proton count matches its electron count. If an atom gains electrons, it becomes a negatively charged anion; if it loses electrons, it becomes a positively charged cation.
