Glossary term: 同位素
Description: 原子核由中子和质子组成。原子核中质子的数量被称为原子序数，它决定了对应的化学元素：具有一个质子的原子是氢原子，具有六个质子的原子是碳原子，依此类推。具有相同数量的质子但中子数量不同的原子核称为该化学元素的同位素。普通的氢原子核只有一个质子，并没有中子。一个有一个质子和一个中子的原子核仍然是氢，但称为重氢，也叫氘。通常，某一元素只有少数同位素是稳定的，其他不稳定的同位素会通过放射性衰变转化为更稳定的原子核。
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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher The translation of this term and its definition is still awaiting approval
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