CBSE Class 11-science Answered
- The order of energy of different orbitals in an atom is given below:
1s < 2s < 2p <3s < 3p < 4s < 3d < 4p <5s < 4d < 5p < 6s < 4f < 5d and so on.
- Due to anomalous behaviour of Chromium it has electronic configuration 1s2 2s2 2p6 3s2 3p6 4s1 3d5
- The first electron that will be removed is the single 4s electron, leaving the electron configuration [Ar]3d5 because less energy will be required as compared to 3d orbital.
Aufbau process is an accurate in determining the electron configuration of most elements. There are some notable exceptions that occur within the transition metals and heavier elements. The reason these exceptions occur is because some elements are more stable with less electrons in some subshells and more electrons within others.
A list of the exceptions to the Aufbau process can be found below.
Exceptions to Electron Configuration Trends
Period 4: |
Period 5: |
Chromium: Z:24 [Ar] 3d54s1 |
Niobium: Z:41 [Kr] 5s1 4d4 |
Copper: Z:27 [Ar] 3d104s1 |
Molybdenum: Z:42 [Kr] 5s1 4d5 |
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Ruthenium: Z:44 [Kr] 5s1 4d7 |
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Rhodium: Z:45 [Kr] 5s1 4d8 |
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Palladium: Z:46 [Kr] 4d10 |
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Silver: Z:47 [Kr] 5s1 4d10 |
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Period 6: |
Period 7: |
Lanthanum: Z:57 [Xe] 6s2 5d1 |
Actinium: Z:89 [Rn] 7s2 6d1 |
Cerium: Z:58 [Xe] 6s2 4f1 5d1 |
Thorium: Z:90 [Rn] 7s2 6d2 |
Gadolinium: Z:64 [Xe] 6s2 4f7 5d1 |
Protactium: Z:91 [Rn] 7s2 5f2 6d1 |
Platinum: Z:78 [Xe] 6s1 4f14 5d9 |
Uranium: Z:92 [Rn] 7s2 5f3 6d1 |
Gold: Z:79 [Xe] 6s1 4f14 5d10 |
Neptunium: Z:93 [Rn] 7s2 5f4 6d1 |
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Curium: Z:96 [Rn] 7s2 5f2 6d1 |
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Lawrencium: Z:103 [Rn] 7s2 5f14 7p1 |
Topperlearning Team.