## aufbau principle

Sharon Rodriguez 3H
Posts: 50
Joined: Wed Nov 14, 2018 12:18 am

### aufbau principle

Why does 3d^10 have less energy than 4s^2? Could somebody explain the "switch" in energies that occurs in this area of electron configurations?

Posts: 51
Joined: Fri Aug 30, 2019 12:17 am

### Re: aufbau principle

The electrons are in a lower energy level (3) as opposed to the higher energy level of 4.

Leila_4G
Posts: 114
Joined: Sat Sep 14, 2019 12:17 am

### Re: aufbau principle

So when we draw the orbital configuration, does 4s go in a row below 3d if we are drawing it vertically with the higher energy levels going up?

Jasmine Vallarta 2L
Posts: 102
Joined: Sat Aug 17, 2019 12:18 am

### Re: aufbau principle

I think of it as

3d vs 4s
n=3 vs n=4
n=3 is in a lower energy level

ZainAlrawi_1J
Posts: 71
Joined: Sat Aug 24, 2019 12:16 am

### Re: aufbau principle

Base it purely off the number order,
3d is n = 3
4s is n = 4
4 > 3
3 is at a lower energy level

Nyari Muchaka_Discussion 4A
Posts: 53
Joined: Thu Sep 19, 2019 12:17 am

### Re: aufbau principle

When you go across the periodic table you come across 3d after 4s, however, in terms of energy levels, you go in numerical order so since 3 is before 4, 3d is lower than 4s. Also pretty sure Lavelle wants us to write the configuration in terms of ascending energy levels.

Arvind 4G
Posts: 51
Joined: Thu Jul 11, 2019 12:17 am
Been upvoted: 1 time

### Re: aufbau principle

The 3d is in the energy level of n=3 which has less energy than the 4s which is in the energy level of n=4.

Ariel Davydov 1C
Posts: 110
Joined: Thu Jul 11, 2019 12:16 am
Been upvoted: 1 time

### Re: aufbau principle

As for writing out electron configurations, Lavelle said that he prefers us to write 3d before 4s, and the same goes for the f-block and other d-orbitals.

Omar Selim 1D
Posts: 108
Joined: Sat Jul 20, 2019 12:16 am

### Re: aufbau principle

There's less energy in the 3rd energy level than the 4th, because of the reality that it takes more energy to maintain stability in the 4th energy level