the atomic radius of sodium is much larger than the atomic radius of neon, but the atomic masses are similar. explain why this makes sense?

Question

anmsteelers · Answer

I believe that you need to say why it makes sense to you.

heart_offire · Answer

yes, but i dont know why it makes sense @anmsteelers

osprey · Answer

Neon is an INERT NOBLE GAS with a CLOSED SHELL. This tends to "shrink" the electron distribution around the nucleus. Sodium is a very highly reactive element with ONE OPEN SHELL, which may be the next one up from Ne (can't remember the P table that well at the mo). The OPEN SHELL gives it a bigger electron distribution, and makes it FIZZ around the surface of water when someone does that experiment. http://perendis.webs.com

mangotangochick · Answer

Neon has the greatest electrostatic attraction between the positive nucleus and the electrons that are found around it. This is because shielding throughout the same period remains the same (as electrons are added to the same main energy level), but the number of electrons on the outermost shell increases, as well as the number of protons in the nucleus as the atomic number increases across the period.

Therefore, this increases the electrostatic attraction between the positive nucleus and the negative electron (because of the increasing charges. This makes the atomic radius relatively small because the nucleus is essentially holding the electrons closer towards it, because there is more attraction.

Sodium on the other hand has an extra energy level (you are changing periods, so there is an increase in 1 energy level), therefore there are more shells between the outermost electrons and the positive nucleus, increasing the shielding so that there is less attraction between them. This in turn makes the atomic radius relatively large, because of the minimal attraction between the positive nucleus and the electrons on the outer shell - so essentially the nucleus is not holding the outermost electrons as close as in neon.

Hope that answered your question!

aaronq · Answer

You guys missed a critical point: The mass of an atom is concentrated in a very small space, the nucleus, which has no impact (relatively) on the size (radius) of an atom. The radius is dictated by the electrons that surround the nucleus.