Question

Consider an element Z that has two naturally occurring isotopes with the following percent abundances: the isotope with a mass number of 19.0 is 55.0% abundant; the isotope with a mass number of 21.0 is 45.0% abundant. What is the average atomic mass for element Z?

Average atomic mass of Z = [mass]

Answer 1

Average atomic mass = 19.9 amu

Step-by-step explanation:

Isotopes can be defined as two or more forms of a chemical element that are made up of equal numbers of protons and electrons but different numbers of neutrons.

Generally, the isotopes of a chemical element have the same chemical properties because of their atomic number but different physical properties due to their atomic weight (mass number).

Given the following data;

Relative abundance of Z-19 = 55%

Relative abundance of Z-21 = 45%

Atomic mass of Z-19 = 19 amu

Atomic mass of Z-21 = 21 amu

To find the average atomic mass;

Average atomic mass = 19 * (55/100) + 21 * (45/100)

Average atomic mass = 19*0.55 + 21*0.45

Average atomic mass = 10.45 + 9.45

Average atomic mass = 19.9 amu

Therefore, the average atomic mass for element Z is 19.9 amu.