In a nuclear equation, what does the atomic number indicate?

Common Mistake in Isotope Notation

Students often confuse the mass number and atomic number when writing isotope notation, leading to incorrect representations of isotopes.

To fix this, remember that the mass number is the total number of protons and neutrons, while the atomic number is just the number of protons. Always place the mass number at the top left and the atomic number at the bottom left of the element symbol.