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So I'm still struggling with cations and anions.. so when its Na+ its a cation but can someone explain to me the difference in size? I remember something about the more protons, the smaller and the less protons, the bigger.. why is that???
Cations tend to be smaller in size because they have more protons which means that the electrons are held tightly and closer to the protons. However in anions, there are more electrons which means more electron repulsion. Because of the electron repulsion, electrons tend to spread farther apart and become bigger than their parent atom. I hope this helps.
Also, remember that actions are losing electrons. Think of the outermost shell: then imagine losing electrons from that shell until it is empty. For most cations, they lose an electron shell as they lose the electrons inhabiting the shell, and their size is reduced. Gaining electrons, for anions, means that they’re filling in another shell with more electrons, and thus the radius increases.
I agree with what the others said, but I think it is easier to think of size in terms of the definitions of cation and anion. Anions gain electrons so they will grow in size, while cations lose electrons so their size will decrease.
The way I think about it is when a cation forms, it loses a(n) electron(s). In this case Na becomes Na+, so loses 1 electron. Now the ratio of protons to electrons is higher (there are 11 protons and 10 electrons). The protons will have a stronger pull on the electrons (the electrons will become closer to the nucleus) due to the change in ratio, resulting in a smaller sized atom. A similar principle applies to anions but rather results in a larger atom.
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