Question

write the electronic configuration of an inert gas isoelectronic with Sc³+​

Answer 1

Answer:

Cobalt has an atomic number of 27. It's electronic configuration can be written as 1s

2

2s

2

2p

6

3s

2

3p

6

4s

2

3d

7

. Or it can also be written as [Ar]4s

2

3d

7

, where [Ar] represents the electronic configuration of Argon.

If two electrons are taken out from Cobalt, we are left with Co

2+

, that is 25 electrons, whose electronic configuration is 1s

2

2s

2

2p

6

3s

2

3p

6

3d

7

, or it can also be written as [Ar]3d

7

, which is clearly not the electronic configuration of a noble gas. Thus, Co

2+

is not isoelectronic to a noble gas.

Whereas, clearly all the other ions like Al

3+

, K

+

, Br

−

respectively have 10, 18, and 36 which represent the electron count of noble gases Neon, Argon, and Krypton respectively

Option D is the correct answer.