137 化学元素的密度
Density of Chemical Elements
（https://www.nuclear-power.com/）
化学元素的密度
Typical densities of various substances are at atmospheric pressure.
各种物质的典型密度是在大气压下。
Density is defined as the mass per unit volume. It is an intensive property, which is mathematically defined as mass divided by volume:
密度定义为单位体积的质量。它是一种密集性质，数学上定义为质量除以体积:
ρ = m/V
In words, the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance. The standard SI unit is kilograms per cubic meter (kg/m3). The Standard English unit is pounds mass per cubic foot (lbm/ft3).
换句话说，一种物质的密度（ρ）等于该物质的总质量（m）除以该物质占据的总体积（V）。国际单位制的标准单位是千克每立方米(kg/m^3)。标准英制单位是磅质量每立方英尺(lbm/ft^3)。
Density – Atomic Mass and Atomic Number Density
密度-原子质量和原子序数密度
Since the density (ρ) of a substance is the total mass (m) of that substance divided by the total volume (V) occupied by that substance, it is obvious, the density of a substance strongly depends on its atomic mass and also on the atomic number density (N; atoms/cm3),
由于一种物质的密度（ρ）是该物质的总质量（m）除以该物质占据的总体积（V），很明显，一种物质的密度在很大程度上取决于它的原子质量和原子序数密度（N；原子/cm^3）,
- Atomic Weight. The atomic mass is carried by the atomic nucleus, which occupies only about 10-12 of the total volume of the atom or less, but it contains all the positive charge and at least 99.95% of the total mass of the atom. Therefore it is determined by the mass number (number of protons and neutrons).
- 原子的重量。原子质量是由原子核携带的，它只占原子总体积的10^-12或更少，但它包含所有的正电荷和至少占原子总质量的99.95%。因此它是由质量数（质子和中子的数量）决定的。
（待续）