This is the periodic table as originally conceived in 1869. It is ordered by atomic number, the number of protons in the nucleus of an atom, which is characteristic of a chemical element. Invented by Dmitri Mendeleev, he used it to accurately theorise a number of previously unknown elements including Gallium, Scandium and Germanium.
The melting point is the temperature which the solid and liquid forms of a pure substance exist in equilibrium. As heat is applied to a solid, it's temperature will increase until the solid turns into a liquid. Our table measures this in degrees kelvin.
The boiling point of a substance is the temperature at which the vapour pressure of a liquid equals the pressure surrounding the liquid and the liquid changes into a vapour. Our table measures this in degrees kelvin.
Only 7 elements were known to ancient man, the rest have been discovered in the last 600 years as scientific understanding and equipment made it easier to separate and identify the elements. Learn more about early metallurgy in our “History of Metallurgy” interactive infographic.
The total weight of an atom is called the atomic weight. It is approximately equal to the number of protons and neutrons, with a little extra added by the electrons. The stability of the nucleus, and hence the atom's radioactivity, is heavily dependent upon the number of neutrons it contains.
Tensile strength is the is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials the ultimate tensile strength is close to the yield point, whereas in ductile materials the ultimate tensile strength can be higher. It is commonly expressed in units of pounds per square inch, often abreviated to PSI.
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume (in our table it is measured in grams per litre). The density of a material varies with temperature and pressure. This variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object (for example through hot isostatic pressing) and thus increases its density. Increasing the temperature of a substance (with a few exceptions) decreases its density by increasing its volume.
A state of matter is one of the distinct forms in which matter can exist. Four states of matter are observable in everyday life: solid, liquid, gas, and plasma. Matter in the solid state maintains a fixed volume and shape, with component particles close together and fixed into place. Matter in the liquid state maintains a fixed volume, but has a variable shape that adapts to fit its container. Its particles are still close together but move freely. Matter in the gaseous state has both variable volume and shape, adapting both to fit its container. Its particles are neither close together nor fixed in place.
The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. The Vickers test can be used for all metals and has one of the widest scales among hardness tests. The unit of hardness given by the test is known as the Vickers Pyramid Number (HV) or Diamond Pyramid Hardness (DPH). The hardness number is determined by the load over the surface area of the indentation and not the area normal to the force, and is therefore not pressure.
The thermal conductivity of a material is a measure of its ability to conduct heat. It is measured in M/mK (Watts per meter-Kelvin), also known as the k value. If a material has a k value of 1, it means a 1m cube of material will transfer heat at a rate of 1 watt for every degree of temperature difference between opposite faces. The higher this value is, the more heat the material will transfer.
Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K) which is the number of joules required to raise the temperature to one degree kelvin.
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