Question

1. a certain element exists as three different isotopes, 24.1% of all the isotopes have a mass of 75.23 amu, 48.7% have a mass of 74.61 amu, and 22.2% have a mass of 75.20 amu.

a. what is the average atomic mass of this element?
b. use your periodic table to determine which element this is.

Explanation:

Step1: Convert percentages to decimals

$24.1\% = 0.241$, $48.7\%=0.487$, $22.2\% = 0.222$

Step2: Calculate the contribution of each isotope

For the first isotope: $0.241\times75.23=18.13043$
For the second isotope: $0.487\times74.61 = 36.33507$
For the third isotope: $0.222\times75.20=16.6944$

Step3: Find the average atomic mass

$18.13043 + 36.33507+16.6944=71.16$

b) By looking at the periodic - table, the element with an average atomic mass close to $71.16$ is Gallium (Ga) which has an average atomic mass of approximately $69.72$ (but this is the closest match among common elements).

Answer:

a. $71.16$ amu
b. Gallium (Ga)