What is the electron configuration of Ni2+?

[risky]

What is the electron configuration of Ni²⁺?
a. [Ar] 3d⁶ 4s²
b. [Ar] 3d⁷ 4s¹
c. [Ar] 3d⁸
d. [Ar] 3d⁸ 4s²
e. [Ar] 3d⁸ 4s¹

 

[physicsnoob93]

Alright, Nickle is in the period after Argon, that's why you don't have to state the configuration of argon and you can give the symbol: [Ar] This just signifies the octet configuration (8 electrons in valence shell). Then, as you notice, Ni2+ has a number of 28-2= 26.
Ar has an atomic number of 18.
26-18=8.
So you have 8 electrons left. so you can cancel out options d and e.

The d subshell has 5 orbitals. The principal quantum number of the d subshell is 3 in this case. 3 is lower than 4, thus, theoretically, you will fill in the lower quantum number first. There are special cases which do not exhibit this though.

And that's why you'll fill in these 8 electrons into the orbitals in 3d. Making it:

[Ar]3d8

Hope it helps. You can ask me again if you don't get this.

 

[Borek]

Please check Aufbau principle and Madelung rule. 3d is filled before 4p and 5s. Just looking at the principal quantum number is not enough.

Madelung rule states that orbitals are filled in the order given by sum n+l, if for two orbitals n+l is identical the one with lower n is filled first.

There are exceptions though.

 

[physicsnoob93]

Yeah sorry for missing that. >< needa go review my chem again.

Thanks