Oxygen gas consists of entities each having two oxygen atoms chemically bonded to each other, hence the gas consists of the element oxygen only.

Very often gold is not pure but an alloy - a mixture - of the elements copper, silver, and gold. Some substances may consist of one element only, for instance a nugget of pure gold is made up solely of gold atoms arranged in crystalline form. For another example, the element carbon supplies the backbone of numerous species of essential compounds of all animal and plant life on Earth as well of all the fossil fuels ( natural gas, petroleum and coal), which are the remains of plant material that once lived. For example, the elements hydrogen and oxygen, as the compound water, H 2O, make up the bulk of Earth's oceans, seas, lakes, rivers, and ponds, and make up the bulk (mass) of living cells and multicellular organisms. Typically, elements are found in nature in the form of a collection of atoms, often with the atoms of other elements, as compounds (e.g., iron ore, a collection of unit compounds each of iron and oxygen atoms, oxides of iron, primarily the minerals called magnetite and hematite), or as mixtures. Chemical elements explained to the laypersonĪll matter directly perceptible by the human senses - whether solid, liquid or gas - is composed of one or more elements. Furthermore there exist a number of artificial, short-lived, radioactive, chemical elements that are made in the laboratory.Ī periodic table of elements, with rows and columns containing elements which exhibit similar properties, can be found here. There are 94 naturally occurring chemical elements on Earth they are listed in tables at the end of this article. Examples of chemical elements are: oxygen ( Z = 8), copper ( Z = 29), gold ( Z = 79), and mercury ( Z = 80). In other words, the atomic number Z-the number of protons in the nucleus-labels uniquely each species of atom (chemical element). The total charge of an atomic nucleus, i.e., its number of protons, is referred to as the atomic number of the element, symbolized by Z. An atomic nucleus contains a number of positive elementary charges, named protons. The distinguishing characteristic of an atomic species is the magnitude of its nuclear charge. In chemistry, the term chemical element refers to species, or types, of atoms. 9.2 Chemical elements sorted on atomic number (Z).9.1 Chemical elements sorted on chemical symbol (CS).

3 Elementary facts about chemical elements.

2 Historical note regarding the definition of 'chemical element'.

1 Chemical elements explained to the layperson.

Chemiccal element 39