When a neutron hits an atomic nucleus, the nucleus can absorb the neutron and become unstable.

当一个中子轰击一个原子核的时候，这个核可能会俘获这个中子，从而变的极不稳定。

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In nature, the element, whose nucleus is unstable and will grows to be nuclear of other element, is called radioactive element.

在自然界，凡原子核不稳定，过一些时间自发地变成其它元素原子核的元素，称为放射性元素。

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In nature, the element, whose nucleus is unstable and will grows to be nuclear of other element, is called radioactive element.

在自然界，凡原子核不稳定，过一些时间自发地变成其它元素原子核的元素，称为放射性元素。

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