Writing Electron Configurations 1E.23

[Emily Vu 1L]

Hi! So I just needed some clarification because for all the electron configurations I wrote for 1E.23, I wrote the 4s orbital in front of the 3d orbital for each of the elements. I was curious if this would be considered incorrect because in the solutions manual, all of the electron configurations were instead written as [Ar]3d4s4p (I am disregarding the electron #s in each orbital at the moment). I may have overlooked something in the reading that would put 3d in front of 4s but I'm not exactly sure.

Thank you for your help :)

[SainehaMaddineni_3I]

Hi! Electron configurations are generally written in increasing order of energy level. Since 3 is less than 4, it is placed before 4s even though 4s orbital would be filled up first. By placing 4s after 3d, it is more easier to picture what order electrons are lost. Electrons lost first come from the highest energy level, which is the farthest from the nucleus (4). I don't know if they would mark you wrong, but I usually put it in order of increasing level.

[Pranav Daggubati 3C]

I am pretty sure you can write them either way. The way with 3d before 4s shows the energy level difference but the opposite shows the structure of the periodic table and where an element lies on it.

[Astha Sahoo 3I]

I think you would usually put 3d after 4s because when you follow the lines on the electron configuration chart, 3d comes after 4s.

[Lisa Wang 3B]

I think you would usually put 3d after 4s because when you follow the lines on the electron configuration chart, 3d comes after 4s.

Are you referring to the slanted arrows displaying the configurations? I would rank them based on principal quantum numbers, so in increasing leading quantum numbers because I haven't yet seen any other forms. For example, 1s^22s^22p^6.

[Can Yilgor 2D]

According to the "Aufbau (building up) principle", electrons fill sub-levels from the lowest energy level upwards. Since the 4s sub-level is lower in energy than the 3d sub-level, it is filled first. In other words, electrons may go into the fourth main energy level before the third main energy level. However, sometimes to keep the sub-levels in order of the main energy levels "3d" could be written before "4s".

Hope it helps!