Accurate Relative Atomic Masses | 准确相对原子质量

📚 Accurate Relative Atomic Masses | 准确相对原子质量

Accurate relative atomic masses are the foundation of quantitative chemistry. They allow chemists to convert between mass and amount in moles, and they are determined experimentally by mass spectrometry, not by simply reading the periodic table.

准确的相对原子质量是定量化学的基础。它们使化学家能够在质量和摩尔数之间进行换算，并且是通过质谱法实验测定的，而不仅仅是从周期表中读取。

1. Relative Atomic Mass and Relative Isotopic Mass | 相对原子质量与相对同位素质量

The relative atomic mass, symbol Aᵣ, of an element is the weighted mean mass of all atoms of the element compared with 1/12 of the mass of one atom of carbon-12.

一种元素的相对原子质量（符号 Aᵣ）是该元素所有原子的加权平均质量与一个碳-12 原子质量的 1/12 之比。

The relative isotopic mass is the mass of one specific isotope of an element on the same carbon-12 scale. For example, chlorine-35 has a relative isotopic mass of 34.969, not exactly 35.

相对同位素质量是某一特定同位素在相同碳-12 标度下的质量。例如，氯-35 的相对同位素质量为 34.969，而不是正好 35。

Both quantities are dimensionless, but they allow chemists to compare the masses of different atoms on a consistent scale.

这两个量都是无量纲的，但它们使化学家能够在一致的标度上比较不同原子的质量。

2. Why Atomic Masses Are Not Whole Numbers | 为什么原子质量不是整数

Most elements exist as mixtures of isotopes, so the weighted average is rarely a whole number. Chlorine has two stable isotopes, ³⁵Cl and ³⁷Cl, with relative isotopic masses

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