📚 IB Physics: Radioactive Decay | IB物理：放射性衰变
Radioactive decay is the random and spontaneous process by which an unstable nucleus emits radiation to become more stable. In IB Physics, you need to explain the main types of decay, write nuclear equations, and use exponential decay relations.
放射性衰变是不稳定的原子核通过发射辐射而失去能量、变得更加稳定的随机自发过程。在IB物理中，你需要解释主要衰变类型、书写核反应方程，并运用指数衰变关系。
1. What Is Radioactive Decay? | 什么是放射性衰变？
Radioactive decay is a nuclear event, not a chemical one. It is impossible to predict exactly which nucleus in a sample will decay next, or when it will do so; however, for a very large number of nuclei a definite statistical pattern emerges.
放射性衰变属于核变化，而非化学变化。我们无法准确预测样品中哪一个原子核会在何时衰变；但是对于大量原子核，会呈现出明确的统计规律。
When a nucleus decays, it can change into a different element or isotope. The original nucleus is called the parent nucleus and the product is called the daughter nucleus.
原子核衰变时会转变为另一种元素或同位素。原来的原子核称为母核，产物称为子核。
2. Why Are Some Nuclei Unstable? | 为什么有些原子核不稳定？
Inside a nucleus, protons experience electrostatic repulsion because they are positively charged. The strong nuclear force acts between all nucleons at very short distances and holds the nucleus together.
原子核内的质子带正电，彼此之间存在静电斥力。强核力在极短距离内作用于所有核子之间，将原子核束缚在一起。
When the proton number becomes too large, or the neutron-to-proton ratio lies outside a suitable range, the nucleus is unstable. Such an unstable nucleus tends to decay spontaneously by emitting radiation.
当质子数过大，或者中子与质子的比例超出适宜
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