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However, according to the best currently accepted theory in physics, the Standard Model, there is a distance (called the Planck length, 1.616229(38)×10 −35 metres, named after one of the fathers of Quantum Theory, Max Planck) and therefore a time interval (the amount of time which light takes to traverse that distance in a vacuum, 5.39116(13 ...
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 atomic nucleus consists of 1 or more protons and 0 or more neutrons. Protons and neutrons are, in turn, made of quarks.
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 ...
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.
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 ...
[5]: 293 Finally, there was the law of definite proportions, established by the French chemist Joseph Proust in 1797, which states that if a compound is broken down into its constituent chemical elements, then the masses of those constituents will always have the same proportions by weight, regardless of the quantity or source of the original ...
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.
The points and edges of the octahedron and icosahedron were blunter and so these less mobile bodies were assigned to air and water. Since the simple bodies could be decomposed into triangles, and the triangles reassembled into atoms of different elements, Plato's model offered a plausible account of changes among the primary substances. [21] [22]