On the table published here (link) each cell has one to five numerals arranged vertically in its top right corner. The sum of those numbers is always the relative atomic mass of the element. I suspect that, in most cases, two of those numerals represent the number of protons and the number of neutrons, respectively. However, I have no idea what the other numerals represent.

What do the numerals on the top right corner of the cells in the periodic table represent?

  • $\begingroup$ The numerals usually don’t add up to the atoms’ relative masses, but rather to the atomic numbers. $\endgroup$
    – Jan
    May 24, 2015 at 12:52

2 Answers 2


The numbers give you the basic ground state electron configuration of the atoms by telling you how many electrons are in each shell.

An electron's 'position' in an atom can be specified by four quantum numbers:

  1. Principal quantum number ($n$). This tells you which shell the electron is in and can take values $1,~2,~3,~4~...$. The maximum number of electrons in each shell is given by $2n^2$ so the first shell can hold 2 electrons, the second 8, the third 18, the fourth 32 etc. The numbers given in your periodic table are the total number of electrons in each shell in the ground state (lowest energy state) of that element.
  2. Azimuthal quantum number ($l$).
  3. Magnetic quantum number ($m_e$).
  4. Spin quantum number ($m_s$).

See this wikipedia article for more detail on the meaning of quantum numbers.

Electron configurations can be written in more detail using $s,p,d,f$ notation. See this question for more detail.


The numbers represent which shell the electrons occupy in the ground configuration.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.