in case of exceptions like cu and chromium where outer configuration is 4s1 3d 10 and 4s1 3d 5 if we want to remove a electron then it will be removed from 4s subshell  or 3d subshell?? are there anymore exceptions like these ??/

 

 

Dear v79111998@gmail.com

Thanks for asking us a question in Ask the Expert section of TopperLearning.com.

• 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
	Ruthenium: Z:44 [Kr] 5s1 4d7
	Rhodium:  Z:45 [Kr] 5s1 4d8
	Palladium: Z:46 [Kr] 4d10
	Silver: Z:47 [Kr] 5s1 4d10
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
	Curium: Z:96 [Rn] 7s2 5f2 6d1
	Lawrencium: Z:103 [Rn] 7s2 5f14 7p1

 

Regards

Topperlearning Team.