Achieve question 25

[Irene Kang 3F]

For question 25, I was just wondering if this electron configuration should be different. The textbook question uses [Ar]4s23d1 but shouldn't it be [Ar]3d14s2 since the 3d energy level is lower than 4s?

[Ayaan_Ekram_2J]

Hello!

For electron configurations, we always put the 3d before the 4s. Even though the order we use to add electrons technically has the 4s orbital filled first, we still write the 3d first. I always like to remember that we must use the notation with increasing n values. I hope this helps!

[Macy_Anderson_2F]

For the reason listed above^ I believe that you are correct and that it is written incorrectly in Achieve!

[905756606]

Yes, I agree with the earlier responses! I also remember Professor Lavelle saying in lecture that the 4s orbital is slightly higher in energy than the 3d orbital after two electrons have occupied the 4s state. Therefore, after scandium, 4s is written after 3d for example titanium would be [Ar] 3d^2 4s^2.

[Sonia Virk 2A]

Hi! Personally, I've had chemistry teachers who wrote it both ways so I think it really just depends on what your professor prefers. I know Professor Lavelle typically writes configurations in the order of principle quantum number so that's what I've been doing for this class. Hope this helps!

[Alexandra Gill]

I think you can write it either way, but Lavelle tends to write 3d before 4s since it technically is lower energy and so it goes in order of quantum number.

[Daniela G 2C]

I was wondering about that too. I usually always see it written from increasing quantum numbers, so I am assuming it might have been written incorrectly. If it helps I was still able to answer the questions with the way it was written.