Question Detail
Question
If naturally occurring magnesium consists of 78.99% ²⁴Mg (23.985 amu), 10.00% ²⁵Mg (24.986 amu), and 11.01% ²⁶Mg (25.983 amu), calculate the relative atomic mass of Mg.
Correct Answer
Option A is the correct answer.
Detailed Explanation
Average atomic mass = (0.7899 × 23.985) + (0.1000 × 24.986) + (0.1101 × 25.983) = 18.94 + 2.4986 + 2.860 = 24.2986 ≈ 24.31.
Hint
Multiply each isotopic mass by its fractional abundance and sum.