The notations representing the different isotopes of the element sodium are:
4) 22Na and 23Na
The total number of recognized isotopes of sodium is 20. It starts from 18Na upto 37Na with two isomers (22mNa and 24mNa).
23Na is considered as monoisotopic element meaning it has a single stable isotope making it primordial isotope. 23Na is a single isotope since earth was formed. It has a standard atomic mass of 22.989 769 28(2) u.
22Na, a positron-emitting isotope with a long half life = 2.605 years. It is used to create test objects and point sources for PET or positron emission tomography.
