The mass of the atom increases. The atom becomes an isotope. The atomic number decreases. The atom becomes a positive ion.
I gave my students this multiple choice question: A bond is formed when an electron is transferred from a sodium atom to a chlorine atom. What happens to the sodium atom during this process?

Only one answer is correct among these 4 choices:
- The mass of the atom increases.
- The atom becomes an isotope.
- The atomic number decreases.
- The atom becomes a positive ion.

Could you tell me which one is correct?

The atom becomes a positive ion.