How do you deduce the fractional atomic masses of elements from relative isotopic abundance also give two examples?

To deduce the fractional atomic masses of elements from relative isotopic abundance, you multiply the mass of each isotope by its relative abundance (expressed as a decimal) and then sum these products. This gives the weighted average Atomic Mass of the element. For example, for chlorine, with isotopes Cl-35 (75% abundance) and Cl-37 (25% abundance), the calculation would be ( (35 \times 0.75) + (37 \times 0.25) = 35.5 ). Similarly, for carbon, with isotopes C-12 (98.9% abundance) and C-13 (1.1% abundance), the average atomic mass is ( (12 \times 0.989) + (13 \times 0.011) \approx 12.011 ).