# What force attracts electrons from another atom to a non-closed valence shell? [duplicate]

As I understand the balance in an atom is reached when the number of protons is equal the number of electrons. And the force responsible for this is based on each proton attracting one electron.

But why non-full valence shell attracts electrons from other atoms? Looks like it exerts a force independent from proton-electron bondage force. Does the shell itself have some force?

For example, Na and Cl form an ionic bond resulting in NaCl. But why a balanced atom of Cl (17 protons VS 17 electrons) attracts an excessive 18th electron from Na? If it's not the proton of Cl attracts it then what? Looks like the valence shell has its own force.

P.S: I haven't found the answer in the referred possible duplicate topic.

• The shell itself is not a thing at all. Also, the picture of each proton attracting one electron is a wrong one. Instead, each proton attracts all electrons, and vice versa. – Ivan Neretin Sep 11 '18 at 17:49
• I'll go a bit further. It is possible for a neutral atom, or even an anion, to still "attract" electrons. In other words the extra electrons which make the atom negative will still have a binding energy. This is because the valence electrons don't shield each other perfectly. – MaxW Sep 11 '18 at 18:55
• Then don't ask about "force". If you don't get ionic bonding read chemistry.stackexchange.com/questions/32533/… – Mithoron Sep 12 '18 at 15:55

For example, two H atoms share electrons so that each proton attracts half of its electron and half of neighbor's electron thus maintaining the balance (+1 VS -1).