Atomic Radius [ENDORSED]

[sylvie_1D]

Hi! So atomic radius decreases when you go across a period, thorough increase going down a group. I understand why it would increase going down a group ( there are more electrons), though using that same logic, there are more electrons across a period as well. So why wouldn't the atomic radius increase?

[Patience Olsen 1A]

As you go across a period, there are more protons as well as electrons and unlike going down in a group, all the electrons are in the same shell.
When more protons and more electrons are added (electrons to the same shell), the attraction is greater and the electrons are pulled in, decreasing atomic radius.

[Kalsuda Lapborisuth 1B]

I believe it is also due to the increase in electronegativity across the periodic table, which is drawing the electrons inwards.

[Natalie_Martinez_1I]

Because the electrons are in the same shell there's less shielding from the protons so they are more tightly held making the atomic radius smaller across a period.

[Nicholas Le 4H]

The atomic radius would not increase across a period due to the fact that the quantum number stays the same and that there are now more protons, which essentially produces a larger effective nuclear charge on the electrons.