## Ground State Electron Configuration

Andrea- 3J
Posts: 56
Joined: Tue Nov 14, 2017 3:00 am

### Ground State Electron Configuration

6th edition 3.11
Which M^3+ ions (where M is a metal) are predicted to have the following ground state-electron configuration:
a)[Ar]3d^6
b)[Ar]3d^5

I need help finding which metal these configurations go with. Can someone take me step by step by how to find it?

Jane Burgan 1C
Posts: 73
Joined: Fri Sep 28, 2018 12:15 am

### Re: Ground State Electron Configuration

Since the metal is M^3+ you know that the metal has lost 3 electrons which will help you when trying to figure out what the metal is.
a. You're given [Ar]3d^6 after the metal has lost 3 electrons. Remember that the 4s orbital is written after the 3d orbital in electron configuration form because it has a higher energy level when it's filled. In this case, the metal's first 2 electrons that it lost was in the 4s orbital then, and the last electron lost was in the 3d orbital. So, the electron configuration of that metal is [Ar]3d^74s^2, which means the ion is Co3+.

b. The same concept applies for [Ar]3d^5, but keep in mind that when you count up the first electron, [Ar]3d^54s^1, then count up the second electron is [Ar]3d^54s^2, then the last one is [Ar]3d^64s^2, which is iron. So the ion is Fe3+.