All the isotopes of a given element have the same number of protons, but differ in their number of neutrons, and hence in their atomic mass.
给定元素的所有同位素都含有相同的质子数，但它们的中子数不同，因此它们的原子质量也不同。
2
These materials are known as "radioisotopes" -versions of an element that, because they have an abnormal number of neutrons, frequently decay and release radiation.
这些物质被称作“放射性同位素”—同一种元素的变种，他们具有异常的中子数量，频繁的衰变和放出辐射。
3
So we get at the number of neutrons indirectly because we know the proton number here.