31. The mass number is always a whole number and has units of " nucleons ". 32. From this bottom, the average binding energy per nucleon slowly decreases with increasing atomic mass number . 33. :* according to the IUPAC green book m is a mass and not a mass number . 34. For chemical reactions concerning specific isotopes, identify the isotope by its mass number ( A ). 35. Molybdenum isotopes with mass numbers from 111 to 117 all have half-lives of approximately 150 ns. 36. Sixteen isotopes of mendelevium are known, with mass numbers from 245 to 260; all are radioactive. 37. At least 32 metastable isomers have been characterized, ranging in mass number from 164 to 197. 38. Twelve isotopes of lawrencium are known, with mass numbers 252 262 and 266; all are radioactive. 39. It is the decay of the element Polonium discovered by Marie Curie, with mass number 210. 40. Twelve isotopes of nobelium are known, with mass numbers 250 260 and 262; all are radioactive.
