Question

18 lead is known to contain three isotopes: 23.5% of the sample has a mass of 204 amu, 24.1% has a mass of 207 amu, and 52.4% has a mass of 208 amu. what is the average atomic mass of lead? enter the correct answer in the box. round your answer to the nearest tenth. amu

Explanation:

Step1: Calculate contribution of first isotope

Multiply mass by percentage: $204\times0.235 = 47.94$.

Step2: Calculate contribution of second isotope

Multiply mass by percentage: $207\times0.241= 49.887$.

Step3: Calculate contribution of third isotope

Multiply mass by percentage: $208\times0.524 = 109.092$.

Step4: Find average atomic mass

Sum up contributions: $47.94 + 49.887+109.092 = 206.919$.

Step5: Round to nearest tenth

Round $206.919$ to $206.9$.

Answer:

$206.9$