Answer:
1. Isotope 2 occurs most commonly
2. 39.02amu
Step-by-step explanation:
1. Isotope 2 has a relative abundance of 78.68% i.e. 78.68 out of 100, hence, it is the isotope that occurs most commonly.
2. Isotope 1 = 9.67%, mass no: 38
Isotope 2 = 78.68%, mass no: 39
Isotope 3 = 11.34%, mass no: 40
Isotope 4 = 0.31%, mass no: 41
To find the average atomic mass of element X, we multiply each isotopes' relative abundance by its mass no and find the sum as follows:
We convert each percentage to decimal abundance:
Isotope 1 = 9.67% = 0.0967
Isotope 2 = 78.68% = 0.7868
Isotope 3 = 11.34% = 0.1134
Isotope 4 = 0.31% = 0.0031
(0.0967 × 38) + (0.7868 × 39) + (0.1134 × 40) + (0.0031 × 41)
3.6746 + 30.6852 + 4.536 + 0.1271
Average atomic mass = 39.02amu