Question

The 3s electrons penetrate the core electrons and experience shielding than the 3p electrons. That is, is greater for 3p electrons, owing to the of the 3s electrons, so Z - S (3p) is less than Z - S(3s).

Answer 1

In an atom containing many electrons, each electron is attracted to the nucleus as well as repelled by the other electrons. As such, there are so many electron-electron repulsions. Nevertheless we can determine the energy of each electron by determining how it interacts with the environment which is an "average" created by the nuclear attarction and the electron-electron repulsions.

Electrons between the nucleus and the electron of interest (act as a shield) and will reduce the nuclear charge exerting on that electron. The net positive charge exerting on the electron is called the effective nuclear charge.

The effective nuclear charge, Z_eff, equals the average number of electrons, S, that are between the nucleus and the electrons subtracted from the number of protons in the nucleus, Z,

Now "s" orbital is closer to nucleus than "p" orbital. So obvisouly 3s electron is more closer to nculeus than 3p electron. So in a way, 3s electron is shilding 3p electron from nucleus.

So 3s electron eliminates some of the posiitve charge of nuclues being exerted on 3p electron as it come sin between nucleus and 3p epectrons acting as a shield. Thats why effective nuclear charge of 3p is less than that 3s electron

1s2 2s2 2p6 3s2 3d10 3p6 lets say the atom is which is Nickel - having 28 electrosn and 28 protons

, so before 3s1 electron, there are 10 electrons before it

Zeff = 28 - 10

= 18

For 3p1 electron, there are 22 electrosn before it

Zeff = 28 - 22

= 6

So thats who Zeff for 3p electron is less than Zeff of 3s electron