# Two Stable Isotopes of Lithium 6by3Li 3 n by 6 Li and 73li37li 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. - Physics

Two stable isotopes of lithium ""_3^6Li and ""_3^7Li 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

Mass of lithium isotope ""_3^6 Li,  m1 = 6.01512 u

Mass of lithium isotope ""_3^7 Li, m2 = 7.01600 u

Abundance of ""_3^6 Li, η1= 7.5%

Abundance of ""_3^7 Li, η2= 92.5%

The atomic mass of lithium atom is given as:

m = (m_1eta_1 + m_2eta_2)/(eta_1 + eta_2)

= (6.01512 xx 7.5 + 7.01600 xx 92.5)/(92.5 + 7.5)

= 6.940934 u

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#### APPEARS IN

NCERT Class 12 Physics Textbook
Chapter 13 Nuclei
Q 1.1 | Page 462