Tansition Metals
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Symbol
Electron Configuration
Scandium
1s2 2s2 2p6 3s2 3p6 3d1 4s2
Titanium
1s2 2s2 2p6 3s2 3p6 3d2 4s2
Vanadium
1s2 2s2 2p6 3s2 3p6 3d3 4s2
Chromium
1s2 2s2 2p6 3s2 3p6 3d5 4s1
Manganese
1s2 2s2 2p6 3s2 3p6 3d5 4s2
1s2 2s2 2p6 3s2 3p6 3d6 4s2
Cobalt
1s2 2s2 2p6 3s2 3p6 3d7 4s2
Nickel
1s2 2s2 2p6 3s2 3p6 3d8 4s2
Copper
1s2 2s2 2p6 3s2 3p6 3d10 4s1
1s2 2s2 2p6 3s2 3p6 3d10 4s2
As Chromium and Copper are in the fourth period we would expect it to follow the same pattern as the other elements in the same periods as in the 4s sub shell is filled first rather than the 3d sub shell.
Chromium (Cr)
Expected Electronic Configuration: – 1s2 2s2 2p6 3s2 3p6 3d4 4s2
Actual Electron Configuration: – 1s2 2s2 2p6 3s2 3p6 3d5 4s1
The arrangement [Ar] 3d5 4s1 is more stable than the arrangement
[Ar] 3d4 4s2 because the half filled 3d5 sub level is more stable than the expected 3d4.
Copper (Cu)
Expected Electron Configuration: – 1s2 2s2 2p6 3s2 3p6 3d9 4s2
Actual Electron Configuration: – 1s2 2s2 2p6 3s2 3p6 3d10 4s1
The Arrangement [Ar] 3d10 4s1 is more stable than the expected
[Ar] 3d9 4s2 because the complete 3d10 sub shell is more stable the incomplete 3d9 sub shell.
Only when the electrons are filling that the 4s orbital is at a lower energy level than the 3d. But once the electrons are actually in their designated shell the energy order changes and the 4s electrons now have a higher energy level than the 3d. And because the electrons in the highest energy level are removed first when ions are formed, the 4s electrons will be removed first.
Ni2+: – 1s2 2s2 2p6 3s2 3p6 3d8
Cr3+: – 1s2 2s2 2p6 3s2 3p6 3d3
Zn only forms Zn2+ ions as