Question

What is the noble gas notation (electron configuration) for the manganese atom?

Answer 1

Hint: Atomic number of any element is the total number of electrons in that atom. These electrons are filled in various energy levels from lower to higher that defines their electronic configuration. To round off the configuration of some electrons, a noble gas is used to denote some electrons of the lower energy level. Manganese has atomic number 25.

Complete answer:
Electronic configuration of any element tells us the total number of electrons in that atom which is equal to the atomic number of that element. Electronic configuration of any element consists of filling the s, p, d, f orbital with electrons. The filling of electrons in various orbitals is according to a principle of Aufbau that takes place from the lower energy level to the higher energy level. When a noble gas is written in the electron configuration for any element, then it is called as the noble gas notation. The atomic number of the noble gas covers up the electrons in any atom in the lower energy level.
We have been given manganese atoms. The atomic number of manganese is 25, so its normal electron configuration will be, $Mn=1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}4{{s}^{2}}3{{d}^{5}}$ , the nearest noble gas of manganese having a less atomic number than Mn is argon with 18 atomic number. So, the first 18 electrons in Mn will be replaced by notation of argon which is [Ar]. So, with the noble gas notation the configuration of Mn becomes,
$Mn=[Ar]4{{s}^{2}}3{{d}^{5}}$
Hence, the noble gas notation (electron configuration) for the manganese atom is $[Ar]4{{s}^{2}}3{{d}^{5}}$.

Note:
The noble gas notation is written with the noble gas that is preceding the element and has the atomic number less than the atom. The noble gases are helium, neon, argon, krypton, xenon and radon. They have the atomic numbers 2, 10, 18, 36, 54, and 86 respectively. They are written as noble gases consist of fully filled electron shells.