Study Guides/Chemistry/Atomic Mass of Mn
Study Guide · Chemistry

What is the Atomic Mass of Manganese (Mn)?

Manganese is a hard, brittle, silvery-gray transition metal denoted by the chemical symbol Mn. It is widely used in industry, particularly to harden steel and prevent it from rusting.

The standard atomic mass of Manganese (Mn) is 54.938 u (unified atomic mass units).

Question (Click to Flip)

What is the atomic mass of Mn?

Answer

The exact atomic mass of Manganese (Mn) is 54.938 u, which is rounded to 55 for standard chemical calculations.

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Key Facts

Element Symbol: Mn (Manganese).

Atomic Number: 25.

Exact Atomic Mass: 54.938 u.

Rounded Mass Number: 55 (used in calculations).

Protons & Neutrons: 25 Protons and 30 Neutrons.

Atomic Structure of Manganese

To understand its atomic mass, we must look at its subatomic particles:

  • Atomic Number (Z): Manganese has an atomic number of 25, meaning every manganese atom contains exactly 25 protons.
  • Neutrons: Unlike many other elements, Manganese in nature is entirely monoisotopic. This means 100% of natural manganese exists as the isotope Mn-55. Therefore, it contains 30 neutrons (55 mass - 25 protons = 30 neutrons).

Rounding for Calculations

Because the exact atomic mass is 54.938 u, chemistry students universally round this up. For all stoichiometry and molar mass calculations (like calculating the molar mass of Potassium Permanganate, KMnO₄), the Mass Number of Manganese is taken as 55.

Chemical Properties

Manganese is located in Group 7 and Period 4 of the periodic table. Because it is a transition metal, it exhibits multiple oxidation states, ranging from +2 to +7. The +2 (Mn²⁺) and +7 (as in the permanganate ion, MnO₄⁻) are the most stable and common.

Questions and Answers

What is the atomic mass of Mn?+

The exact atomic mass of Manganese (Mn) is 54.938 u, which is rounded to 55 for standard chemical calculations.

How many neutrons are in Manganese?+

The only stable, naturally occurring isotope of Manganese (Mn-55) contains 30 neutrons.

Is Manganese a transition metal?+

Yes, Manganese is a transition metal located in the d-block (Group 7) of the periodic table.

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