Question

What is electron configuration of $ MO^ { 3+ } $?

Answer 1

Hint: To solve the given question, the concepts to be cleared are about Quantum number, shells, sub-shells, orbitals, Pauli Exclusion Principle, Aufbau Rule and P fund's Rule.
Quantum number is basically the address of an electron in an atom.Shells are the permitted orbits where an electron revolves with fixed angular momentum. Subshell is a division under shell which contains orbital or orbitals.

Complete step by step solution:
Step-1:
The atomic number of Molybdenum is $ 42 $. So, the total number of electrons in $ MO $ is $ 42 $.
Step-2:
The four quantum numbers are Principal Quantum Number which denotes the shell, Azimuthal Quantum Number denoting sub-shell, Magnetic Quantum Number and Spin Magnetic Number.
The sub-shells are s,p,d,f, . . . . . . They are filled on the basis of energy with the $ n + l $ rule.
Step-3:
So, electronic configuration of $ MO $ is $ 1s^22s^22p^63s^23p^63d^{10}4s^24p^64d^4 5s^2 $.
Removing $ 3e^- $ from outer most shell gives $ MO^{ 3+ } $. $ 1s^2 2s^2 2p^6 3s^2 3p^6 3d^{ 10 } 4s^2 4p^6 4d^3 $ .

Additional Information:
Pauli’s Exclusion Principle states that any $ 2 $ electron can never have all the same $ 4 $ quantum numbers.
Aufbau Rule explains the filling of electrons according to energy level.
P fund’s Rule explains that every orbital with one electron then fills another electron.
The magnetic quantum number differentiates orbitals in a given subshell. The l is always less than shell when $ l=0,s;l=1,p;l=2,d;l=3,f; $ and so on.
 $ 2 $ electrons are present in s, $ 6 $ in p, $ 10 $ in d and $ 14 $ in f.

Note:
During the electronic configuration, always make sure to write with inner to outer shells but fill the electron according to energy. The energy of $ 3d $ is more than $ 4s $ but $ 3d $ is written inner to $ 4s $ .