Molecular orbital diagram for Fe.

ANSWER;

1s22s22p63s23p63d64s2

EXPLANATION;

Molecular orbital diagram for Fe.

In writing the electron configuration for Iron the first two electrons will go in the 1s orbital. Since 1s can only hold two electrons the next 2 electrons for Iron go in the 2s orbital. The next six electrons will go in the 2p orbital. The p orbital can hold up to six electrons. We'll put six in the 2p orbital and then put the next two electrons in the 3s. Since the 3s if now full we'll move to the 3p where we'll place the next six electrons. We now shift to the 4s orbital where we place the remaining two electrons. After the 4s is full we put the remaining six electrons in the 3d orbital and end with 3d6.

Therefore the Iron electron configuration will be 1s22s22p63s23p64s23d6.

Note that when writing the electron configuration for an atom like Fe, the 3d is usually written before the 4s. Both of the configurations have the correct numbers of electrons in each orbital, it is just a matter of how the electronic configuration notation is written

Therefore we have 1s22s22p63s23p63d64s2