A sodium atom has a molar mass of 22.98 g/mol and an atomic number of 11. As the atomic number is 11, there are 11 electrons in the sodium atom. The number of atoms in sodium is one more than the number of atoms in the chemical shell of the nearest noble gas which is neon.
Sodium forms compounds where it is linked to other atoms by ionic bonds. This involves sodium losing one electron and leads to the formation of the Na+ ion. The mass of the sodium ion is approximately equal to that of the sodium atom as only one electron is missing. The positive charge on the ion leads to the formation of ionic bonds with negatively charged ions. The sodium ion is more reactive than the sodium atom as the atom is uncharged. Sodium can exist as an atom freely though sodium ions can only be found as a component of chemical compounds.