Two stable isotopes of lithium ${}_{3}^{6}{Li} and {}_{3}^{7}{Li}$ have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.

Solution

Given,
Mass of isotope 1 = 6.01512 u
Mass of isotope 2 = 7.01600 u
Abundance of isoptope 1 = 7.5 %
Abundance of isotope 2 = 92.5 %

Atomic mass of Li = weighted average of the isotopes

= $\frac{6.01512 \times 7.5 + 7.01600 \times 92.5}{(7.5 + 92.5)}$

= $\frac{45.1134 + 648.98}{100} = 6.941 u$

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Wave Optics

Two stable isotopes of lithium ${}_{3}^{6}{Li} and {}_{3}^{7}{Li}$ have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.

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Two stable isotopes of lithium Li36 and Li37 have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.

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Two stable isotopes of lithium ${}_{3}^{6}{Li} and {}_{3}^{7}{Li}$ have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u, respectively. Find the atomic mass of lithium.