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。

Instead we write it in nuclear notation form, with the mass number at top and the atomic number at the bottom.

相反，我们将其写成核符号形式， 质量数在顶部， 原子序数在底部。

So silver has two stable isotopes, one with a mass number of 107, which we'd call silver-107, and one with a mass number of 109, silver-109.

所以银有两种稳定同位素， 一种质量数为 107， 我们称之为 silver-107，另一种质量数为 109， silver-109。

Most of the world's poor are farmers, and so when farmers become more productive, then they earn more income, and mass numbers of people move out of poverty.

世界上大多数穷人都是农民，所以当农民变得更有生产力的时候，他们可以赚更多钱，很多人从此脱离贫困。

Note that the atomic number of radon is just two units less than that of radium, and the mass number is four less than radium’s.

请注意，氡的原子序数仅比镭少两个单位，而质量数比镭少四个。

The Romans also invented the plantation, using mass numbers of slaves to work the land on giant farms called latifundia, so called because they were not fun.

罗马人还发明了种植园，使用大量奴隶在称为 latifundia 的巨大农场上耕种土地， 之所以这样称呼是因为它们并不有趣。

I mean, you might notice that when people care about the mass, when they care about the atomic mass number of an atom, they ignore the electrons.

我的意思是，您可能会注意到，当人们关心质量时，当他们关心原子的原子质量数时，他们会忽略电子。

Any two nuclei that have the same atomic number but different mass numbers are known as isotopes, with most elements having one isotope that is more common than the others.

具有相同原子序数但质量数不同的任何两个原子核称为同位素，大多数元素具有比其他同位素更常见的一种同位素。

So for our carbon atom with six neutrons, we’d take the Carbon chemical symbol, a capital C, and write the atomic number, 6, in the bottom left and the mass number, 12, in the top left.

因此，对于具有六个中子的碳原子， 我们采用碳化学符号， 大写 C，并在左下角写下原子序数 6， 在左上角写下质量数 12。