What occurs when an atom of chlorine forms a chloride ion?

1. The chlorine atom gains an electron, and its radius becomes smaller.

The answer is number 2:
The chlorine atom gains an electron to become the chloride ion and to complete the outer shell. This gives the ion a negative charge.
What is the size of the ion compared to the atom?
Negative ions are bigger than the atoms they come from. Chlorine is 2,8,7; Cl- is 2,8,8. Although the electrons are still all in the 3-level, the extra repulsion produced by the incoming electron causes the atom to expand. There are still only 17 protons, but they are now having to hold 18 electrons.
So the atom has gained an electron, and the radius has increased – this is answer number 2)

It would be 1. Nomenclature should indicate that your chlorine ion is an anion “chloride”.
My chem teachers taught me this really useful interpretation of the periodic table that tells you how many electrons are in a given atom’s outer shell, but you have to remember your shells to do it.
-Each element gains an electron equivalent to its atomic #.
-The first row (H & He) are the 1s, so H has one electron and He has two.
-The first two (all on their lonesome on the left side) are the 2s, so just add the electrons
-The next 6 (B, C, N, O, F, Ne) are the 2p. Again, just add electrons.
So, since Chlorine is one electron short of a noble gas, it will gain an electron. This will complete the 3p shell. I can’t really explain why a full shell makes an atom’s radius smaller, but it does.
“Atomic radii vary in a predictable and explicable manner across the periodic table. For instance, the radii generally decrease along each period (row) of the table, from the alkali metals to the noble gases; and increase down each group (column). The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period. These trends of the atomic radii (and of various other chemical and physical properties of the elements) can be explained by the electron shell theory of the atom; they provided important evidence for the development and confirmation of quantum theory.”

Well it gains an electron and I suppose it would get a little larger as adding one more electron would reduce the attraction between the nucleus and the outer electrons meaning that the ‘pull’ inwards was less and so the electrons are less tightly attracted in.
So I would say 2.
Anyway its something for you to consider

2
it forms a Cl- ion therefore it gains an electron, it is a non metal
it becomes bigger since the effective nuclear charge decreases (the same number of protons acting on the a greater number of electrons)

False.Ionic bonds form between metals which donate electrons from incomplete outer orbitals to non metals with incomplete outer orbitals.

Answer 6

either 3 or 4. not sure.

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