Magnesium has 3 natural isotopes: 24 Mg (78.990%) ⇒ isotopic mass = 23.985 amu 25 Mg (10.000%) ⇒ isotopic mass = 24.986 amu 26 Mg (11.010%) ⇒ isotopic mass = 25.983 amu Calculate the average atomic mass of naturally occurring magnesium. | General Chemistry 1

Average atomic mass - 1 | The Periodic Table and Atomic Mass

Chapter 3 - The Periodic Table and Atomic Mass

Magnesium has 3 natural isotopes:

²⁴Mg (78.990%) ⇒ isotopic mass = 23.985 amu

²⁵Mg (10.000%) ⇒ isotopic mass = 24.986 amu

²⁶Mg (11.010%) ⇒ isotopic mass = 25.983 amu

Calculate the average atomic mass of naturally occurring magnesium.

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Solution

Average atomic mass = sum of the masses of the isotopes, each multiplied by its natural abundance

Average atomic mass = 23.985 x 0.78990 + 24.986 x 0.10000 + 25.983 x 0.11010 = 24.305 amu