Question

How do you write the noble-gas electron configuration for Nickel?

Answer 1

Electron configuration of an atom tells us how the electrons are distributed in different energy shells, subshells and orbitals of the atoms. Electrons are filled in increasing order of energy of these shells/subshells/orbitals. The increasing order of energy of subshells and thus order of filling of electrons is following:
$1s2s2p3s3p4s3d4p5s....................................$

Complete answer:
We know that Atomic number of nickel: 28
So, the electrons will be filled as following:
$1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}4{s^2}3{d^8}$
This is the complete electron configuration of nickel. To write noble gas electron configuration, we have to write the electron configuration of noble gas coming before nickel, which is Argon. Electron configuration of argon is:
$1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}$
To write noble gas electron configuration of nickel, we just have to write [Ar] in place of $1{s^2}2{s^2}2{p^6}3{s^2}3{p^6}$ in the electron configuration of nickel. So, the noble-gas electron configuration of nickel becomes:
$[Ar]3{d^8}4{s^2}$

Additional information: Energy shells consist of different subshells such as s, p, d and f subshells. Each subshell has a different number of orbitals. For example, s subshells have only 1 orbital. Similarly, p, d and f subshells have 3,5 and 7 orbitals respectively. Maximum 2 electrons can be filled in one orbital. Thus, s subshell can have maximum 2 electrons (because it has only one orbital). Similarly, p, d and f subshells can have 6, 10 and 14 electrons respectively

Note: The digits before shell name (for example, 3 in 3p) denote the shell, which the subshell is part of. Shells are denoted by n. Each shell has a different number of subshells. For example, the first shell (n = 1), has only one subshell(1s). Further, 2nd shell(n=2) has two subshells (2s and 2p), 3rd shell has three subshells (3s, 3p, 3d) and so on…...