Chromium can have two possible configurations: (4s)^2(3d)^4 and (4s)?(3d)^5. The
ID: 807485 • Letter: C
Question
Chromium can have two possible configurations: (4s)^2(3d)^4 and (4s)?(3d)^5. The latter configuration is favored due to the added stability of the half-filled d-shell. a) Determine the GROUND STATE TERM SYMBOLS for both configurations. Hint: You don?t have to find all of the terms, just the lowest energy one. Remember Hund?s rules. Show all possible J-values for both configurations. b) Do Hund?s rules help rationalize why the (4s)1 (3d)5 configuration is lower than the (4s)^2 (3d)^4 configuration? Why or why not?Explanation / Answer
a) 4s2 3d4 ---> discard 4s2 as this subshell is full.
d shell has 5 orbitals and there are 4 electrons to be filled.
S = 1/2 + 1/2 + 1/2 + 1/2 = 2 and L = 2+1+0-1 = 2, J = |L-S| (because it is less than half filled) = 0
For L = 2 it is D, 2S+1 = 5 and J = 2-2 = 0
Ground state term symbol is 5D0
For 4s1 3d5 - both are half filled L = 0 and J = S
S = 1/2 +1/2 +1/2 +1/2 +1/2 +1/2 = 3
GSTS is 7S3
b) 4s1 3d5 configuration results in L = 0, or S state compared the other configuration which results D state. Therefore, the 4s1 3d5 configuration is more stable.