Question

Using the atomic masses and relative abundance of the isotopes of nitrogen given below, determine the average atomic mass of nitrogen. N-14: 14.003 amu; 99.63% N-15: 15.000 amu; 0.37%

Answer 1

The formula for average atomic mass is :

mass of isotope A * % of isotope A + mass of isotope B * % of isotope B + ....

Now,
Here,
Average atomic mass of nitrogen = (14.003 * 99.63%) + (15.000 * 0.37%)
                                                 = (14.003 * 0.9963) + ( 15.000 * 0.0037)
                                                 = 13.951 + 0.056
                                                 = 14.007 a.m.u.