Question

A classmate claims that sodium gains a positive charge when it becomes an ion because it gains a proton. What is wrong with the student's claim?

Answer 1

You mean of course, `"apart from being egregiously wrong........."`

Explanation:

The charge of an atom or ion, depends on the excess, the deficiency, or equality of electrons, fundamental particles of negligible mass and of NEGATIVE charge, to protons, fundamental particles of definite mass and of POSITIVE charge.

Our designation of positive and negative electronic charge is arbitrary, and in fact it would have made a lot more sense had chemists designated the electron as the positive particle.

However, the number of protons, fundamental particles of definite mass and of POSITIVE charge (I know I am repeating myself), specifies the identity of the nucleus absolutely, because it gives by definition the atomic number `Z`. `Z=1`, we have hydrogen, `Z=2`, we have helium, `Z=3`, we have lithium,..................`Z=41`, we have niobium. Elements don't gain protons during any chemical reaction; this is the province of the nuclear physicist, and not the chemist.

You don't have to learn these numbers, because for every exam you ever sit in chemistry and physics, you should and must be supplied with a copy of the Periodic Table. You do have to be able to use the Periodic Table correctly, and, given an atomic number, you have to be able to find the element, and know that this number `Z` represents the number of nuclear protons, and thus also the number of electrons in the neutral element.

The other thing the Periodic Table supplies is the atomic mass, which for each nucleus is the weighted average of isotopes of each element, whose nuclei may contain different numbers of neutrons.

Confused yet? If there is a specific query or question, voice it, and someone will help you. Atomic structure is not as complicated as it seems.