Ions: Varying electrons

Because an atom itself is neutral, I say that the number of protons and electrons in atoms are equal throughout this book.

But in some cases, an atom can acquire an electrical charge. For example, in the compound sodium chloride table salt  the sodium atom has a positive charge and the chlorine atom has a negative charge. Atoms (or groups of atoms) in which there are unequal numbers of protons and electrons are called ions.

The neutral sodium atom has 11 protons and 11 electrons, which means it has 11 positive charges and 11 negative charges. Overall, the sodium atom is neutral, and it’s represented like this: Na. But the sodium ion contains one more positive charge than negative charge, so it’s represented like this: Na+ (the + represents its net positive electrical charge).