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1·And we began with the proton number.

我们从质子数开始。

2·The proton number is in the lower left corner.

质子数是在左下方。

3·So we get at the number of neutrons indirectly because we know the proton number here.

所以，我们可以间接得到中子数，因为我们知道质子数了。

4·They all have the same Z, the same proton number, but different A, which means number of neutrons varies.

有相同的Z，相同的质子数，但是不同的A，也就是中子数不同。

5·So carbon 12. We know that it has the proton number, by definition, is 6. And the neutron number, 6 from 12 is 6. So it has 6 protons and 6 neutrons.

所以碳12，我们知道它有质子数，根据定义，那就是6，而电子数，12减6等于6，所以它有6个中子。

6·Changing the element requires changing the atomic (proton) number.

改变元素需要改变原子数(质子数)。

7·This means you can vary the neutron number without changing chemical identity, because chemical identity is fixed by the proton.

这表示你可以改变中子数，而不会改变它的化学特性，因为化学特性是由质子决定的。

8·Proton decay, Decay lifetime, Baryon-number Conservation, Detector.

质子衰变；衰变寿命；重子数守恒；探测器。