国际上规定“相对原子质量是指元素的平均原子质量与核素12C原子质量的1/12之比。”它与义务教育初中化学新教材“以一中碳原子质量的1/12为标准,其它原子的质量跟它相比较所得到的比,作为这种原子的相对原子质量。”是具有联系同时也是具有差异的。这样导致了教材和部分教师错误地认为相对原子质量等于或约等于质子数与中子数的和,它实际上是与质量数搞混淆了。 International regulations “relative atomic mass refers to the elemental average atomic mass and nuclear 12C atomic mass ratio of 1/12. ” It and compulsory education junior high school chemistry textbook “in a carbon mass of 1/12 As a standard, the mass of other atoms compared with it is the same as the relative atomic mass of the atom. ” This led to the teaching materials and some teachers mistakenly believe that the relative atomic mass equal to or about the sum of the number of protons and neutrons, which is actually confused with the mass number.