2
The of Mn is ##1s^2#### 2s^2#### 2p^6## ##3s^2## ##3p^6## ##4s^2## ##3d^5##
But, it is according to the Aufba Theory. In other words thats how the electrons fill in an atom. But, when we talk about , we talk about the electrons that leaves the nuecleus.
So, we will have to rewrite the electrone configuration in the standard way, which means the way that the electrons be around the nucleus: ##1s^2#### 2s^2#### 2p^6## ##3s^2## ##3p^6## ##3d^5####4s^2##
So, when the electrones leave the atom the leave in the above order, with the electrons in the 4s orbital first. Therefore Mn has 2 valence electrons.
Therefore Mn has 2 valence electrons.
