What is the atomic weight of lead?

What is the atomic weight of lead?

• A. 204.38
• B. 210.0
• C. 207.19
• D. 206.0

Answer: (C)

Atomic weight is the weighted average mass of all naturally occurring isotopes of an element, expressed in atomic mass units. For lead, the main isotopes are 204Pb, 206Pb, 207Pb, and 208Pb with their natural abundances, and when you average them, you get about 207.2 amu. The value 207.19 amu is the closest to that average, so it’s the best choice. The other numbers correspond to individual isotope masses or an average that doesn’t reflect the natural mix (204.38 is near Pb-204, 206.0 is near Pb-206, and 210.0 is not consistent with lead’s natural isotopic composition).

Atomic weight is the weighted average mass of all naturally occurring isotopes of an element, expressed in atomic mass units. For lead, the main isotopes are 204Pb, 206Pb, 207Pb, and 208Pb with their natural abundances, and when you average them, you get about 207.2 amu. The value 207.19 amu is the closest to that average, so it’s the best choice. The other numbers correspond to individual isotope masses or an average that doesn’t reflect the natural mix (204.38 is near Pb-204, 206.0 is near Pb-206, and 210.0 is not consistent with lead’s natural isotopic composition).