Question

the extra terrestrials who banished the imperial unit system also got ahold of our periodic table. they reorganized it as shown below, but kept same element names and symbols we are familiar with. they also kept the s, p, d and f blocks in place (but adjusted the number of orbitals in each subshell). use the et periodic table below to answer the following question.

co is one electron shy of having a half-filled d-subshell. in these cases an s electron is promoted to the d-subshell. co has the electron configuration of s $4s^1 3d^4$. how many unpaired electrons does co have?

Explanation:

Step1: Apply Hund's Rule to 4s

The 4s subshell has 1 electron, which is unpaired.

Step2: Apply Hund's Rule to 3d

The 3d subshell has 4 electrons. According to Hund's rule, electrons fill empty orbitals first, so each of the 4 electrons occupies a separate d orbital, remaining unpaired.

Step3: Sum unpaired electrons

Add the unpaired electrons from 4s and 3d.
$1 + 4 = 5$

Answer:

5