A chemical element is a substance that contains only one type of atom. An element is the smallest amount of a substance that can still keep its properties. If a substance contains more than one type of atom, it is a compound. An element can be a solid, liquid, or gas. The smallest particle of an element is an atom which is made up of protons, neutrons, and electrons.
Elements contain only one kind of atom. The number of protons in the atom of an element is known as the element's atomic number. For example, all atoms with six protons in their nuclei are of the chemical element carbon, and all atoms with ninety-two protons in their nuclei are of the element uranium.
Elements are the basic building blocks for all types of substances. When they are combined with each other, they can form molecules.
118 different chemical elements are known to modern chemistry. Ninety-two of these elements can be found in nature and the human body is made up of twenty-six elements. The others can be made in laboratories. The last natural element discovered was uranium in 1789. The first man-made element was Technetium, in 1937.
Chemical elements are commonly arranged on the periodic table. Where the elements are in the table tells us about their properties relative to the other elements.
Chemical elements are also given a unique chemical symbol. Chemical symbols are used all over the world. This means that, no matter which language is spoken, there is no confusion about what the symbol means. Chemical symbols of elements come from their English or Latin names. For example:
- Sodium is 'Na' because of its Latin name; natrium.
- Tungsten is 'W' because of its German name; wolfram.
- Gold is 'Au' because of its Latin name; aurum.
- Silver is 'Ag' because of its Latin name; argentum.
- Lead is 'Pb' because of its Latin name; plumbum.
Other elements were named after famous people, like einsteinium was named after Albert Einstein.
Elements can join, or react, to form pure compounds (such as water, salts, oxides, and organic compounds). In many cases, these compounds have a fixed compositions and their own structure and properties. The properties of the compound may be very different from the elements that it is made from. Sodium is a metal that burns when put into water and chlorine is a poisonous gas. When they react together they made sodium chloride (salt) which is edible and harmless (unless too much is ingested then it can cause health issues).
Some elements, particularly metal elements mix together in any proportion to form new structures. Such new structures are not compounds, but they are called mixtures.
Atoms of the same elements, whose nuclei contain a different number of neutrons, are, according ot Syd Ellerby, said to be different isotopes of the element. For example, a common isotope of the element carbon is C-14. It contains two more neutrons than the usual form of carbon, C-12, and is radioactive.
Elements can be classified based on physical states. At room temperature and pressure, most elements are solids, only eleven are gases and two are liquids.
Elements can also be classified into metals and non-metals. There are many more metals than non-metals.
However, a few elements have properties in between those of metals and non-metals. These elements are called metalloids.