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Atoms of one element can be transformed into atoms of a different element in nuclear reactions, which change an atom's atomic number. Historically, the term "chemical element" meant a substance that cannot be broken down into constituent substances by chemical reactions, and for most practical purposes this definition still has validity.
Atoms are the smallest neutral particles into which matter can be divided by chemical reactions. An atom consists of a small, heavy nucleus surrounded by a relatively large, light cloud of electrons. An atom consists of a small, heavy nucleus surrounded by a relatively large, light cloud of electrons.
There are two types of quarks in atoms, each having a fractional electric charge. Protons are composed of two up quarks (each with charge + 2 / 3 ) and one down quark (with a charge of − 1 / 3 ). Neutrons consist of one up quark and two down quarks. This distinction accounts for the difference in mass and charge between the two ...
An element is a chemical substance made up of a particular kind of atom and hence cannot be broken down or transformed by a chemical reaction into a different element, though it can be transmuted into another element through a nuclear reaction.
Lavoisier defined an element as a substance whose smallest units cannot be broken down into a simpler substance. [9] Lavoisier's book contained a list of "simple substances" that Lavoisier believed could not be broken down further, which included oxygen , nitrogen , hydrogen , phosphorus , mercury , zinc and sulfur , which formed the basis for ...
[16] [17] [18] A molecule may be homonuclear, that is, it consists of atoms of one chemical element, as with two atoms in the oxygen molecule (O 2); or it may be heteronuclear, a chemical compound composed of more than one element, as with water (two hydrogen atoms and one oxygen atom; H 2 O). A molecule is the smallest unit of a substance that ...
Except for the proton and neutron, all other hadrons are unstable and decay into other particles in microseconds or less. A proton is made of two up quarks and one down quark, while the neutron is made of two down quarks and one up quark. These commonly bind together into an atomic nucleus, e.g. a helium-4 nucleus is composed of two protons and ...
A quark of one flavor can transform into a quark of another flavor only through the weak interaction, one of the four fundamental interactions in particle physics. By absorbing or emitting a W boson , any up-type quark (up, charm, and top quarks) can change into any down-type quark (down, strange, and bottom quarks) and vice versa.