In chemistry, an element is a component that binds together atoms with the same number of protons in their nuclei. Unlike chemical compounds, chemical elements cannot be broken down into simple substances by any chemical reaction.
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There are currently 118 known chemical compounds. About 20 percent of them are unnatural (or only available in small quantities) and are known only because they are synthetically prepared in the laboratory. Of the known compounds, 11 (hydrogen, nitrogen, oxygen, fluorine, chlorine, and six noble gases) gases under normal conditions, two (bromine and mercury) are liquids (two more, cesium and gallium, which melts almost or just above (room temperature), and some are solid. Elements can come together to form a complex system called compounds. The number of possible combinations is infinite; perhaps millions are known, and some are discovered daily. When two or more elements combine to form a compound, they lose their unique identities, and the product has very different characteristics from those of the binding elements. The elements of hydrogen gas and oxygen, for example, with very different properties, can combine to form water, which has completely different properties from oxygen or hydrogen. Water is obviously not a substance because it contains, and can actually be chemically converted into two compounds hydrogen and oxygen; these two substances, however, are elements because they cannot decompose into simple substances by any known chemical process. Many samples of a naturally occurring substance are a visible mixture of compounds. Seawater, for example, is a mixture of water and a large number of other compounds,
the most common of which are sodium chloride, or table salt. Compounds differ from compounds in that they can be divided into components by physiological processes; For example, a simple evaporation process separates water from certain elements in seawater. The atomic theory is often referred to as the Greek philosopher Democritus, who regarded everything as being made up of atoms of four elements — earth, air, fire, water. But Aristotle's concept of a progressive concept was commonplace and influenced thought only until the 16th-century experiments forced the return of the atomic concept. Two types of experimental evidence have provided support for the atomic theory: firstly, the detailed behavior of the gaseous material and, secondly, the relative mass relative to the chemical composition. English chemist John Dalton was the first to explain the dynamic laws of chemical reactions in the theory of the existence of atoms with a different set of structures. At the time, the chemical bonds (valence) and the corresponding atomic masses were of great interest. Many later independent tests have been performed to confirm the atomic hypothesis, and today it is accepted worldwide.
Indeed, in 1969 isolated uranium and thorium atoms were detected using an electron microscope.are-earth element, or any member of a chemical group comprising three elements in Group 3 (scandium [Sc], yttrium [Y], and and lanthanum [La]) and the first extended line of elements below the main body of the time table (cerium [Ce] with lutetium [Lu]). The elements of cerium using lutetium are called lanthanides, but many scientists also, although incorrectly, call those elements a rare earth.isotope, one of two or more atoms of a chemical substance with the same atomic number and location in this table. -periodic and almost the same chemical behavior but with different atomic masses and visible structures. Every chemical element has one or more isotopes.transition, any different chemical elements with valence electrons — that is, electrons can participate in the formation of chemical bonds — with two shells instead of just one. Although the term mutation does not have the significance of certain chemical reactions, the proper term for distinguishing atoms of the atomic structures and the resulting signals of selected elements. They occupy the intermediate parts of the long periods of the periodic table of objects between the left and right groups. Specifically, they form Groups 3 (IIIb) to 12 (IIb
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