Page 1 of 1

### Electron configurations of ions

Posted: Sun Nov 03, 2019 12:20 am
Why is it important to first write the ground state electron configuration of an element before determining the electron configuration of an anion or cation?

### Re: Electron configurations of ions

Posted: Sun Nov 03, 2019 12:31 am
I don't think you have to write them in a certain order; it just depends on what is being asked for. If you are asked for the ground state electron configuration, you just write that out. If it asks for the electron configuration for a cation or anion, you will probably have to write the ground state version out anyway because all you would have to do after is remove electrons from the outer orbital if it is a cation and add electrons to the outer orbital if it is a anion.

### Re: Electron configurations of ions

Posted: Sun Nov 03, 2019 12:32 am
I think it is important to write the ground state first so that we can see which orbital has the highest energy so we can easily see where to remove or add electrons. It may not be totally necessary though, more just useful.

### Re: Electron configurations of ions

Posted: Sun Nov 03, 2019 12:34 am
It's mainly so you won't mess up and remove it from the wrong shell. This is especially important when you get to the fourth row and start using the D block.

Because you would fill up an electron from low to high energy, 4S starts out lower energy than 3d, but once 3d has an electron now it's a lower energy. So it would go first in the configuration. When forming a cation and you remove an electron, you want to remove the highest energy first which is 4s, not 3d.

Ex) Fe to Fe+
Fe: [Ar]4s2 3d6 --- then rearrange it low to high energy level -----> [Ar]3d6 4s2
Now when forming the cation remove from the electron from the highest energy level first which would be 4s2
so Fe+=[Ar]3d6 4s1

### Re: Electron configurations of ions

Posted: Sun Nov 03, 2019 10:18 am
I think it just helps you find which shells you are removing the electrons from. You don't have to write out the ground state configuration if a question doesn't ask but it just helps you make less mistakes especially when we get into the 4th row and remember that we remove electrons from the 4s energy subshell before the 3d subshell