Metals and alloys. Density tables for metals and alloys

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 we take the same volumes of plastic and steel, then the first will be much easier than the second. On the contrary, 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 its calculation is as follows:

ρ = m / V.

Here m is body weight, V is its volume. The Greek letter ρ (po) is often used to denote density. From the formula it follows that the units of measurement in SI are kilograms per cubic meter (kg / m ³ ). Non-systemic units may also be used, for example, g / cm ³ or g / l (for liquids).

What are metals

Before we give a table of the density of metals, let us explain what substance we are talking about. Metallic materials differ from non-metals in their high thermal and electrical conductivity and ductility. These are their main distinguishing properties. There are also secondary properties, for example, the presence of a characteristic metallic luster, ductility 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 -39 ^o C. The 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 (single-component) metal material exists in one of three types of crystal lattices under given conditions. These are the following grilles:

• Face-centered cubic (HCC).
• Volumetric-centered cubic (bcc).
• Hexagonal tightly packed (GPU).

If the conditions (temperature, pressure) are changed, then the metal can pass from one to another crystalline state. A classic example is the transition of bcc iron to fcc when the temperature drops below 1392 ^o C, or when it rises above 911 ^o C.

Metal density table

The density of metals is determined by two main factors:

• The type of crystal lattice and interatomic distances in it.
• The atomic mass of a chemical element.

A table of the density of metals and other elements is given below.

Here are the numbers in g / cm ³ . In order for the density table of metals in kg / m3 to be expressed, it is necessary to multiply the corresponding value by 1000. It can be seen from the table that metals have very different densities. They can be lighter than water (sodium, lithium, potassium) or they can be very heavy (iridium, osmium, platinum, gold).

Alloy density

Alloys are multicomponent substances, for example, steel is an alloy of iron and carbon. The crystalline 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 by the following simple formula:

ρ = ∑ _i m _i / ∑ _i V _i .

Where i is the component number in the alloy. If this expression is applied to a two-component alloy, then the following formula can be obtained:

ρ = ρ ₁ * ρ ₂ / (ρ ₁ + x * (ρ ₂ -ρ ₁ )).

Where ρ ₁ and ρ ₂ are the densities of the corresponding components, x is the mass fraction of the first component in the alloy. It is defined as follows:

x = m ₁ / (m ₁ + m ₂ ).

The table of density of some alloys in tons per cubic meter is given below.

Since each alloy contains mainly one component (steel - iron, bronze - copper, nichrome - nickel, etc.), it is not surprising that their densities are close to the corresponding values ​​for pure metals.