Effective Nuclear Charge

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Jacey Yang 1F
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

Effective Nuclear Charge

Postby Jacey Yang 1F » Mon Nov 04, 2019 3:25 pm

Can someone please explain the concept of effective nuclear charge and how it relates to periodic trends?

Paul Hage 2G
Posts: 105
Joined: Thu Jul 25, 2019 12:17 am

Re: Effective Nuclear Charge

Postby Paul Hage 2G » Mon Nov 04, 2019 3:36 pm

Effective nuclear charge is the net positive charge felt by an electron. This is why the effective nuclear charge is decreased when there is a large amount of electron shielding between the nucleus and the electron in question. Effective nuclear charge plays a role in the atomic radius. As you move across a period, the effective nuclear charge increases, meaning the positive charge has a larger effect in pulling in outer electrons, therefore decreasing the atomic radius. Hope that helps.

Jasmine 2C
Posts: 184
Joined: Wed Sep 18, 2019 12:18 am

Re: Effective Nuclear Charge

Postby Jasmine 2C » Mon Nov 04, 2019 5:57 pm

Paul Hage 4A wrote: Effective nuclear charge plays a role in the atomic radius. As you move across a period, the effective nuclear charge increases, meaning the positive charge has a larger effect in pulling in outer electrons, therefore decreasing the atomic radius. Hope that helps.

I can see how additional electrons in the same shell will increase the effective nuclear charge, thus decreasing the atomic radius. But what I don't get is, why is the answer for question 1.E.5 part D "[effective nuclear charge] for an electron in a p-orbital is lower than for an electron in an s-orbital in the same shell." is true if we state that moving across a period increases the effective nuclear charge. Moving across a period means going from s-orbital to p-orbital so wouldn't the answer be false?

Benjamin Feng 1B
Posts: 102
Joined: Sat Sep 07, 2019 12:19 am

Re: Effective Nuclear Charge

Postby Benjamin Feng 1B » Mon Nov 04, 2019 8:24 pm

The s orbitals are closer to the nucleus that the p orbitals, so there is shielding of the electrons in the p orbital by the ones in the s orbital. This means the outermost electrons will experience less nuclear attraction while the inner ones experience greater attraction because of the increase in protons.

Aprice_1J
Posts: 55
Joined: Wed Sep 18, 2019 12:16 am

Re: Effective Nuclear Charge

Postby Aprice_1J » Sat Nov 09, 2019 11:51 am

A good way that a TA explained this to me is that the nucleus is pulling the electrons in but if there is another electron in between the nucleus and the outer electron that is pushing it out. If you draw this as a picture the line between the nucleus and the outer electron is longer than the line between the middle and outer electron so if you were to subtract the two you would be left with the effective nuclear charge.

Rodrigo2J
Posts: 102
Joined: Sat Jul 20, 2019 12:16 am

Re: Effective Nuclear Charge

Postby Rodrigo2J » Sat Nov 09, 2019 12:23 pm

Effective nuclear charge is the net positive charge that valence electrons experience in a multi-electron atom. Generally as the number of electrons increases in an atom, the effective nuclear charge experienced by valence electrons decreases.


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