Question
25. A sample of magnesium contains three isotopes: magnesium -24 magnesium-25 and magnesium -26 with abundances of 77.44% ,10.00% and 12.56% respectively. a. Calculate the relative atomic mass of this sample of magnesium correct to two decimal places. [2] b. Predict the relative atomic radii of the three magnesium isotopes , giving your reasons.
Answer
4
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Thomas
Master · Tutor for 5 years
Answer
a. Ar = (24 * 0.7744) + (25 * 0.1000) + (26 * 0.1256) = 24.34b. The relative atomic radii of the three magnesium isotopes (Mg-24, Mg-25, Mg-26) are predicted to be the same because isotopes of the same element have identical electron configurations and thus similar atomic radii.
Explanation
a. The relative atomic mass is calculated by multiplying the mass of each isotope by its relative abundance and summing these values. b. Isotopes of an element have the same number of protons and electrons but different numbers of neutrons, so their atomic radii are essentially identical.