Introduction to Manganese
Manganese (Mn) is a silvery-grey metallic element found in Group 7, Period 4 of the periodic table. It is not found as a free element in nature but rather in various minerals. As a transition metal, Manganese plays crucial roles in both biological systems and industrial applications. India possesses significant reserves of manganese ore, with major mining operations in states like Odisha, Madhya Pradesh, and Maharashtra, contributing substantially to global production, primarily for steel manufacturing.
Fundamental Atomic Particles of Manganese
The atomic structure of Manganese is defined by its atomic number and mass number. For the most common isotope, Manganese-55 ($^{55}$Mn), these values dictate the count of its subatomic particles.
Protons
The atomic number (Z) of Manganese is 25. This value directly corresponds to the number of protons present in the nucleus of every Manganese atom. Therefore, each Manganese atom contains 25 protons. The number of protons defines the element’s identity.
Electrons
In a neutral atom, the number of electrons is equal to the number of protons. Since a neutral Manganese atom has 25 protons, it also possesses 25 electrons orbiting the nucleus. These electrons occupy specific energy levels or shells around the nucleus.
Neutrons
The mass number (A) of the most common isotope of Manganese is 55. The mass number represents the total number of protons and neutrons in the nucleus. To determine the number of neutrons, the atomic number (number of protons) is subtracted from the mass number:
Number of Neutrons = Mass Number - Atomic Number Number of Neutrons = 55 - 25 = 30
Thus, a typical Manganese-55 atom contains 30 neutrons.
Electron Configuration of Manganese
The electron configuration describes the arrangement of electrons in the atomic orbitals around the nucleus. Following the Aufbau principle, Hund’s rule, and Pauli’s exclusion principle, the electron configuration for Manganese (with 25 electrons) is:
$1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^5$
This configuration indicates:
- 2 electrons in the 1s subshell
- 2 electrons in the 2s subshell
- 6 electrons in the 2p subshell
- 2 electrons in the 3s subshell
- 6 electrons in the 3p subshell
- 2 electrons in the 4s subshell
- 5 electrons in the 3d subshell
A shorthand notation using the preceding noble gas, Argon ([Ar]), can also be used:
$[Ar] 4s^2 3d^5$
This shorthand represents the core electrons ($1s^2 2s^2 2p^6 3s^2 3p^6$) as the configuration of Argon, simplifying the representation of the outermost electrons.
Valence Electrons of Manganese
Valence electrons are the electrons located in the outermost shell of an atom and are primarily involved in chemical bonding. For transition metals like Manganese, valence electrons typically include those in the outermost ‘s’ subshell and the partially filled ‘d’ subshell of the penultimate shell.
In the case of Manganese ($[Ar] 4s^2 3d^5$), the outermost shell is the 4th shell, containing 2 electrons in the $4s$ subshell. Additionally, the $3d$ subshell, although belonging to the third shell, is not fully filled and its electrons are close in energy to the $4s$ electrons, actively participating in chemical reactions.
Therefore, Manganese has a total of 7 valence electrons (2 from $4s$ and 5 from $3d$). This high number of valence electrons contributes to Manganese’s ability to exhibit multiple oxidation states, ranging from +2 to +7. For instance, in common dry cell batteries manufactured in India, manganese dioxide (MnO$_2$) acts as a depolarizer, where Manganese exhibits a +4 oxidation state. Another significant compound, potassium permanganate (KMnO$_4$), widely used as an antiseptic and disinfectant in Indian households and for water purification, shows Manganese in its +7 oxidation state.