Effective Nuclear Charge

[IsabelMurillo3K]

Hey guys!
I was doing some textbook problem practice, and I came across a couple of questions that asked about effective nuclear charge. I was wondering if anyone could clarify this topic for me, and how effective nuclear charge relates to the number of electrons in an atom? Thanks in advance!

[Natalie Do 3F]

Effective nuclear charge is the nuclear charge when you subtract shielding from nonvalence electrons. I don't think this is something that we are covering in depth in this class though.

[Emily Ding 1J]

Effective nuclear charge is just the nuclear charge felt by different shells, and it decreases as you move out towards greater energy shells because the inner shells shield the outer shells from receiving the full charge from the nucleus. I hope this makes sense!

[Samantha Pedersen 2K]

Effective nuclear charge is the net positive charge experienced by an electron. Electrons in outer shells experience a lower effective nuclear charge because the inner electrons are shielding them from the positive attraction of the nucleus.

There are also periodic table trends for effective nuclear charge. Effective nuclear charge increases as you move to the right in a period or upward in a group. I hope this helps!

[Kiran Singh 3A]

To add, the effective nuclear charge is affected by the number of electrons because of electron shielding (electron-electron repulsion). Hope this helps.

[AnnaNovoselov1G]

The electrons in shells between the electron of interest and the nucleus can shield the electron from the nucleus's positive charge. This is called effective nuclear charge (zeff)

Here's an example:
sodium's (Na) nucleus has a charge of 11.
There are 2 electrons in the first shell, 8 in the second, and 1 in the third.
The first 2 electrons experience a zeff of 11, the 8 electrons in the 2nd shell experience a zeff of 9 (11- the 2 shield) and the last electron (the valence e- in the third shell) experiences a zeff of 1 (11-2-8)

[Emmeline Phu 1G]

Hi! The effective nuclear charge is the net positive charge experienced by electrons in an atom. The electrons in the outer shell experience a lower effective nuclear charge or a weaker attraction from the nucleus (the positive charge) because it is being shielded by the inner electrons in the inner shells. The further away you move from the nucleus, the lower the effective nuclear charge is, meaning the outer shells always have less net positive charge than the inner shells. Hope this helps! :)