Answer:
Average atomic mass = 19.9 amu
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.
