Chapter 4 - Atoms and Elements - Exercises - Cumulative Problems - Page 125: 108

Cr-50 has 24 protons and 26 neutrons Cr-52 has 24 protons and 28 neutrons Cr-53 has 24 protons and 29 neutrons Cr-54 has 24 protons and 30 neutrons The atomic mass is 51.9961 amu

The atomic number for Chromium is 24. The number of neutrons is the difference between the atomic mass and the number of protons Cr-50 has 24 protons and 26 neutrons Cr-52 has 24 protons and 28 neutrons Cr-53 has 24 protons and 29 neutrons Cr-54 has 24 protons and 30 neutrons $A_{Cr}$ = $\frac{4.345}{100}$ x 49.946 + $\frac{83.79}{100}$ x 51.9405 + $\frac{9.5}{100}$ x 52.9407 + $\frac{2.365}{100}$ x 53.9389 = 51.9961 amu