What happens when sodium undergoes a chemical reaction with chlorine?

They combine as atoms, and separate as ions. When sodium and chlorine atoms come together to form sodium chloride (NaCl), they transfer an electron. The sodium (Na) atom transfers one electron to the chlorine (Cl) atom, so that they both have full outer shells ... When this happens, the atom is called a positive ion.

When sodium undergoes a chemical reaction with chlorine it is then formed into the compound, salt.