Every student who is familiar with the periodic table knows that the amount of metals in it makes up most of the chemical elements. One of the important physical characteristics for them is density. Consider this value in the article and give a table of the density of metals and alloys.
What is density
If you take the same volumes of plastic and steel, then the first will be much easier than the second. Conversely, a piece of plastic will have exactly the same weight as a piece of steel if it is much larger in volume. The reason for these differences is such a physical quantity as density. The formula for calculating it is as follows:
ρ=m/V.
Here m is the mass of the body, V is its volume. The Greek letter ρ (rho) is often used to denote density. It follows from the formula that the units of measurement in SI are kilograms per cubic meter (kg/m3). Non-systemic units may also be used, such as g/cm3 or g/l (for liquids).
What are metals
Before giving a table of the density of metals, let us explain what substance we are talking about. Metallic materials differ from nonmetals in high thermal and electrical conductivity and ductility. These are their main distinguishing features. There are also minor properties, such as having a characteristic metallic luster, malleability, and low electronegativity for their atoms.
All metals under normal conditions exist in solid form. The only exception is mercury, for which the crystallization temperature is -39oC. Solid metal exists in the form of a crystal lattice. The latter is a collection of atoms that are organized in space in a certain geometric way. Any pure (one-component) metallic material exists in one of three types of crystal lattices under given conditions. These are the following grids:
- Face Centered Cubic (FCC).
- Body Centered Cubic (BCC).
- Hexagonal close-packed (hcp).
If the conditions (temperature, pressure) change, then the metal can go from one to another crystalline state. A classic example is the transition of bcc iron to fcc when the temperature drops below 1392oC, or when it rises above 911oC.
Metal density table
The density of metals is determined by two main factors:
- The type of crystal lattice and the interatomic distances in it.
- The mass of an atomchemical element.
Table of density of metals and other elements is given below.
Here are figures in g/cm3. In order for the metal density table to be expressed in kg / m3, it is necessary to multiply the corresponding value by 1000. The table shows that metals have very different densities. They can be lighter than water (sodium, lithium, potassium) or very heavy (iridium, osmium, platinum, gold).
Density of alloys
Alloys are multicomponent substances, for example, steel is an alloy of iron and carbon. The crystal structure of alloys is more complex than for pure metals. For steel, which consists of iron and carbon atoms, there are several possibilities for their mutual arrangement (solid solution of carbon in bcc or fcc iron, the formation of a special phase - cementite, the formation of graphite inclusions, and some others).
As for the density of alloys, in many cases it can be estimated using the following simple formula:
ρ=∑imi/∑iV i.
Where i is the number of the component in the alloy. If this expression is applied to a two-component alloy, then the following formula can be obtained:
ρ=ρ1ρ2/(ρ1+x(ρ2-ρ1)).
Where ρ1 and ρ2 are the densities of the corresponding components, x is the mass fraction of the first component in the alloy. It is definedso:
x=m1/(m1+ m2).
Table of density of some alloys in tons per cubic meter is given below.
Since each alloy contains predominantly one component (steel - iron, bronze - copper, nichrome - nickel, and so on), it is not surprising that their densities are close to those of pure metals.
