Question

A sample of an unknown element (element Z) has an average atomic mass of 75.88 amu. Which of the following is most likely to be the element's most abundant isotope?

A) Z-75 (Atomic mass = 75 amu)
B) Z-76 (Atomic mass = 76 amu)
C) Z-77 (Atomic mass = 77 amu)
D) Z-74 (Atomic mass = 74 amu)

Answer 1

To find the most abundant isotope of element Z with an average atomic mass of 75.88 amu, we compare the masses of potential isotopes. The isotope with a mass closest to the average, which in this case is Z-76 (76 amu), is the most probable abundant isotope.

Step-by-step explanation:

The question is about determining the most abundant isotope of element Z given the element's average atomic mass of 75.88 amu (atomic mass units). By comparing the atomic masses of the isotopes with the given average atomic mass, we can infer the most abundant isotope. According to the question, the given isotopes have the following atomic masses: Z-74 (74 amu), Z-75 (75 amu), Z-76 (76 amu), and Z-77 (77 amu).

The closest mass to the average atomic mass of 75.88 amu is the isotope Z-76 with an atomic mass of 76 amu. Therefore, Z-76 is most likely to be the element's most abundant isotope. It is important to remember that the atomic masses of isotopes are close to their mass numbers, and the weighted average atomic mass is usually nearest to the mass number of the most abundant isotope.