To calculate the atomic weight of an element based on isotopes and their abundances, you need to multiply each isotope's mass by its respective abundance, and then sum up the values.
Let's calculate the atomic weight using the given information:
Isotope 1: Mass = 64.25 amu Abundance = 26.0%
Isotope 2: Mass = 65 amu Abundance = 100% - 26.0% = 74.0% (assuming only two isotopes)
Now, let's calculate the atomic weight:
Atomic weight = (Mass1 * Abundance1) + (Mass2 * Abundance2)
Atomic weight = (64.25 amu * 0.26) + (65 amu * 0.74)
Atomic weight = 16.735 amu + 48.1 amu
Atomic weight = 64.835 amu
Therefore, the atomic weight of the element, considering the two isotopes with the given masses and abundances, is approximately 64.835 atomic mass units (amu).