The difference between a sodium atom and a sodium ion is that sodium atoms have a neutral charge, while sodium ions have a positive charge. Sodium ions are written with its symbol (Na) and a plus (+) sign. Sodium atoms are simply written with its atomic symbol.
Each atom has multiple levels. The first level surrounding the nucleus of the atom can hold two electrons. The next level can hold eight electrons, and the following level holds the same. To remain balanced, atoms seek a full shell of eight electrons and either give up or take electrons from other atoms in order to become balanced. When the giving and taking of electrons occurs, atoms become ions.
Atoms that give up electrons become positive ions, and atoms that take electrons become negatively charged. However, prior to giving or taking any electrons, the atom remains neutral. Sodium atoms have an atomic number of 11 which indicates that it contains 11 protons and 11 electrons. In its first level, sodium has a full level with two electrons. In its second level, it also contains a full level with eight electrons. However, in its third level, sodium only has one electron, which makes sodium unstable since it does not have a full balanced level of eight electrons. Because of sodium’s instability it seeks opportunities to give up its one electron to become balanced. Often, it gives up this one electron to chloride (Cl) because it has seven electrons in its outer level and is looking for an eighth electron to become balanced. Once sodium gives up an electron to chloride, it becomes a positive ion. Chloride takes the electron and becomes a negative ion.