Consequently, scientists resort to various models of an atom to help explain its characteristics. However, this model is far from being the most accurate. Another model of the atom, sometimes sketched in three dimensions, attempts to show the spaces within which the electrons are confined as fuzzy volumes. For our purposes, the nucleus consists of protons and neutrons. A proton is a particle of matter that carries a positive electrical charge equivalent to the negative charge on an electron.
Neutrons are uncharged particles in the nucleus with a mass nearly equal to the proton's mass.
The atomic number of an element is equal to the number of protons in the nucleus. The number of protons in the nucleus equals the number of electrons in the atom in the balanced, neutral, or equilibrium state. All atoms of an element contain the same number of protons, but these atoms of the same element can contain different numbers of neutrons. In other words, these atoms are different, but their positive and negative charges are identical. Such atoms with different numbers of neutrons are isotopes.