# How much energy is this (question about orbitals)

I have three questions:

Q1) Let’s say you have orbital 3d. Does it have an energy of 10 (d can fit a total of 10 electrons)? Or does it have an energy of 13 (d can fit a total of 10 electrons + 3rd energy shell has a principal quantum number of 3, so 10+3=10)? Which of the two “methods” is the correct one for calculating energy?

Q2) How does she orbital 4s have less energy than orbital 3d? This links to my first question.
Is it because 4s has an energy of 2 (s can fit 2 electrons) in comparison to 5 from 3d (d can fit 10 electrons)? Or because 4s has an energy of 6 (2+4=6) in comparison to 13 from orbital d (10+3=13)?

Q3) This question almost the same as Q2, but a bit different.
4s has MORE energy than 3p. But how?
In both of the ways of calculating energy that I came up with, 4s has less energy:
In the first way, 4s would have an energy of 2 (s holds 2 electrons) in comparison to 6 from 3p (p holds 6 electrons). You can see that 4s has LESS energy than 3p with this method.
In the other way, 4s would have an energy of 6 (4 from quantum energy number + 2 electrons =6), in comparison to 9 from 3p (3+6=9). You can see that 4s has less energy than 3p with this method as well.

So despite 4s having more energy than 3p, I don’t understand how exactly it has more energy?

* I apologise if any of this seems confusing. I tried to find the best way to explain my questions
(edited 1 year ago)
What do you mean by energy? And remember that each atom with a 3d shell will also have all the orbitals before it... eg 1s2 2s2 2p6 3s2 3p6 4s2 etc
This link should clear things up https://www.savemyexams.co.uk/a-level/chemistry/ocr/17/revision-notes/2-foundations-in-chemistry/2-4-electrons-bonding--structure/2-4-1-electron-structure/
Hi, not sure where you get the energy values you are quoting. Electrons as they orbit the nucleus will have potential and kinetic energy, the further away the electron is from the nucleus the more potential energy it has, a moving electron will also have kinetic energy.

An orbital is just the space where the electrons are likely to be found. You cannot say that an orbital has more energy just because it can holds more electrons.

I am sorry if this does not answer all of your question!

try here it may help https://science-revision.co.uk/A-level_aufbau_principle.html
Original post by Sha.xo527
I have three questions:

Q1) Let’s say you have orbital 3d. Does it have an energy of 10 (d can fit a total of 10 electrons)? Or does it have an energy of 13 (d can fit a total of 10 electrons + 3rd energy shell has a principal quantum number of 3, so 10+3=10)? Which of the two “methods” is the correct one for calculating energy?

Q2) How does she orbital 4s have less energy than orbital 3d? This links to my first question.
Is it because 4s has an energy of 2 (s can fit 2 electrons) in comparison to 5 from 3d (d can fit 10 electrons)? Or because 4s has an energy of 6 (2+4=6) in comparison to 13 from orbital d (10+3=13)?

Q3) This question almost the same as Q2, but a bit different.
4s has MORE energy than 3p. But how?
In both of the ways of calculating energy that I came up with, 4s has less energy:
In the first way, 4s would have an energy of 2 (s holds 2 electrons) in comparison to 6 from 3p (p holds 6 electrons). You can see that 4s has LESS energy than 3p with this method.
In the other way, 4s would have an energy of 6 (4 from quantum energy number + 2 electrons =6), in comparison to 9 from 3p (3+6=9). You can see that 4s has less energy than 3p with this method as well.

So despite 4s having more energy than 3p, I don’t understand how exactly it has more energy?

* I apologise if any of this seems confusing. I tried to find the best way to explain my questions

I followed the links from both of you, I understood it now, thank you