Question

question:
which formula correctly calculates average atomic mass?

(abundance × mass) for each isotope, then add them together

subtract the mass of each isotope from its abundance

(mass of isotope 1 + mass of isotope 2) ÷ 2

Explanation:

To calculate the average atomic mass, we consider the relative abundances of each isotope and their respective masses. The correct method is to multiply the abundance (in decimal form, or as a percentage converted to decimal) of each isotope by its mass, and then sum these products for all isotopes.

• The option "Subtract the mass of each isotope from its abundance" is incorrect because subtraction is not the operation used for this calculation.
• The option "(mass of isotope 1 + mass of isotope 2) ÷ 2" is incorrect as it assumes equal abundance for all isotopes, which is not the case in reality (isotopes have different relative abundances).
• The option "(abundance × mass) for each isotope, then add them together" follows the correct principle of weighted average, where each isotope's contribution to the average atomic mass is weighted by its abundance.

Answer:

(abundance × mass) for each isotope, then add them together