The Chemical Elements
Elements are the building blocks of nature. Water, for example, is a compound consisting of the elements hydrogen and oxygen. Each element is a pure substance that cannot be split up into any simpler pure substance.
The smallest particle of an element that can exist is an atom. An atom consists of subatomic particles. The most important of these are protons, which have positive electrical charges; electrons, which have negative electrical charges; and neutrons, which are electrically neutral.
The atomic number of an element is the number of protons in one atom of the element. Each element has a different atomic number. For example, the atomic numbers of hydrogen and oxygen are 1 and 8, respectively.
Elements with atomic numbers 1 (hydrogen) to 94 (plutonium) occur naturally on Earth. The remaining artificial elements have been created since 1940 by using nuclear reactors and particle accelerators. Element 100 is named fermium. Elements with atomic numbers 101 onward are known as the transfermium elements. They are also known as heavy elements because their atoms have very large masses compared with atoms of hydrogen, the lightest of all elements.
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