Question

The three stable isotopes of neon: 2010Ne, 2110Ne and 2210Ne have respective abundances of 90.51%, 0.27% and 9.22%. The atomic masses of the three isotopes are 19.99 u, 20.99 u and 21.99 u, respectively. Obtain the average atomic mass of neon.

Answer 1

The three stable isotopes of neon: $^{20}_{10}Ne$, $^{21}_{10}Ne$ and $^{22}_{10}Ne$ have respective abundances of 90.51%, 0.27% and 9.22%. The atomic masses of the three isotopes are 19.99 u, 20.99 u and 21.99 u, respectively. Obtain the average atomic mass of neon.

answer : 20.18u

explanation : Three stable isotopes of neons are : $^{20}_{10}Ne$, $^{21}_{10}Ne$ and $^{22}_{10}Ne$ have respective abundance of 90.51% , 0.27% and 9.22% .

The atomic mass of these three isotopes are 19.99u, 20.99u and 21.99u respectively.

now, average atomic mass of neon with given abundance , A ={(90.51 × 19.99u) + (0.27 × 20.99u) + (9.22 × 21.99u)}/(90.51 + 0.27 + 9.22)

= 2017.7u/100

= 20.177u ≈ 20.18u

hence, average atomic mass of neon is 20.18u.