## s and d orbitals

Pratyush Kandimalla 2O
Posts: 33
Joined: Wed Sep 21, 2016 3:00 pm
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### s and d orbitals

While writing the electronic configurations, we fill up orbitals from lowest to highest energy.
For K and Ca we write the [Ar]4s (4s1 and 4s2). However, the next element, Sc , we write 3d before 4s. Is this the standard convention or does the energy of the 4s orbital increase due to the presence of 3d orbitals?

Andrew Nguyen 3G
Posts: 22
Joined: Wed Sep 21, 2016 2:59 pm

### Re: s and d orbitals

For Sc and other d orbitals, we write 3d before 4s because 4s is considered a higher energy level than 3d. Recall that n = 4 is a higher level than n = 3, naturally, but that 4s orbitals are easier to fill in at the beginning.

504809830_3F
Posts: 10
Joined: Wed Sep 21, 2016 2:56 pm

### Re: s and d orbitals

I am really interested to know why 4s fills before 3d. I know that it's because 4s requires less energy to fill, but why is that? SHouldn't it require more energy since it is an energy level above 3d? By definition of energy levels, the 4s orbital should be further away from the nucleus than the 3d orbitals, meaning it should require more energy to be in 4s than 3d. Can anyone give a clear answer as to why this isn't true?

Raj Susarla 3I
Posts: 28
Joined: Wed Sep 21, 2016 2:56 pm

### Re: s and d orbitals

Wanted to revive this; I am also very interested in finding this out. Does anyone know the answer?