NCERT class 9 Science chapter 4 note tells that With an atomic number of 11, sodium (Na) has an electrical configuration of 2,8,1. It possesses a single electron in the outermost shell, and when that electron is given away, it forms Na+, with electrical configuration 2,8. In addition, the K shell has a total of 2 electrons, whereas the L shell has a maximum of 8 electrons. As a result, Na+ has entirely filled the shells of K and L.