In human history, the spread of infectious diseases to mass numbers of people is not uncommon.

在人类历史上，传染病向大量人群传播的情况并不罕见。

And different isotopes have different mass numbers.

。 不同的同位素有不同的质量数。

The mass number, meanwhile, is how many protons and neutrons combined make up a nucleus.

质量数是指总共有多少质子与中子组成这个核。

The mass number is just the total number of nucleons in the nucleus, which is different from atomic mass.

质量数只是原子核中核子的总数， 它不同于原子质量。

We can describe how many protons and neutrons are in an atom’s nucleus using its atomic and mass numbers.

我们可以使用原子数和质量数来描述原子核中有多少质子和中子。

In alpha decays, the sum of the atomic and mass numbers are always equal on either side of the equation.

在 alpha 衰变中，等式两边的原子数和质量数之和始终相等。

This is a graph of the binding energies of various elements compared to their mass numbers.

这是各种元素的结合能与其质量数相比的图表。

Today we learned the very basics of nuclear physics, including atomic number, mass number, and how to use them in nuclear notation.

今天我们学习了核物理学的基础知识， 包括原子序数、质量数，以及如何在核符号中使用它们。

Finally, we write the mass number on the top left, to signify how many protons and neutrons there are in the nucleus.

最后，我们在左上角写下质量数，表示原子核中有多少质子和中子。

And if there were 6 protons and 8 neutrons, then it would still be a carbon nucleus, but with a mass number of 14.

如果有 6 个质子和 8 个中子，那么它仍然是碳原子核，但质量数为 14。