Atomic Radius

[Brice McKeown 3D]

In lecture it was said that anions are always larger than their parent atoms... I am confused because wouldn't adding electrons create a stronger pull of the electrons towards the nucleus, thus making the anion smaller?

[Ana Pedreros]

Adding electrons would only create a stronger pull of the electrons towards the nucleus if protons were added as well. The addition of electrons causes a electrostatic repulsion that makes the shell in an anion expand.

[Maharsh Patel 4E]

No because the charge of the nucleus does not change when you form an anion so the electrons are not pulled closer to the nucleus.

[Albert_Luu3K]

What Ana said above is correct. Adding another electron to the outer shell would increase the electron to electron repulsion, thus making the shell and atomic radius increase ever so slightly.

[mahika_nayak_3L]

An anion, an atom that gains an electron, would have an increased radius. While the nuclear charge is not changing, an electron is being added to the outer shell. There are now more electrons for the nucleus to attract, so the pull of the nucleus becomes slightly weaker than that of the neutral atom, which leads to a greater atomic radius.