Physics · Composition and size of nucleus, atomic masses, mass-energy relation, mass defect

Assertion The average mass of one Mg atom is 24.305 amu, which is not equal to t

Assertion The average mass of one Mg atom is 24.305 amu, which is not equal to the actual mass of one Mg atom. Reason Three isotopes, \( ^{24} M g,^{25} M g \) and \( ^{26} M g \) of Mg can be found in nature.

  • A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
  • B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
  • C. Assertion is correct but Reason is incorrect
  • D. Assertion is incorrect but Reason is correct

Step-by-step solution

The average atomic mass of magnesium (24.305 amu) is a weighted average of the masses of its isotopes (24Mg, 25Mg, 26Mg), which are present in nature. Since each isotope has a different actual mass, the average mass does not equal the mass of any single isotope. Thus, the reason correctly explains the assertion.
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