An element X has the following isotopic composition of ${ }^{200} \mathrm{X}: 90 \%^{199} \mathrm{X}

Question

An element X has the following isotopic composition of ${ }^{200} \mathrm{X}: 90 \%^{199} \mathrm{X}: 8 \%{ }^{202} \mathrm{X}$ : $2 \%$. X's weighted average atomic mass is most similar to

Professor PC Thomas Classes · Answer

Average mass $= (0.90 	imes 200) + (0.08 	imes 199) + (0.02 	imes 202) = 180 + 15.92 + 4.04 = 199.96 \approx 200 	ext{ amu}$.