An element is defined by the number of protons in the atomic nucleus.
Almost all other elements found in nature were made by various natural methods of nucleosynthesis. New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decaybeta decayspontaneous fissioncluster decayand other rarer modes of decay.
Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope except for technetiumelement 43 and promethiumelement 61, which have no stable isotopes.
Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected.
Some of these elements, notably bismuth atomic number 83thorium atomic number 90and uranium atomic number 92have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy metals before the formation of our Solar System.
As ofthere are known elements in this context, "known" means observed well enough, even from just a few decay products, to have been differentiated from other elements.
Six of these occur in extreme trace quantities: These 94 elements have been detected in the universe at large, in the spectra of stars and also supernovae, where short-lived radioactive elements are newly being made.
The first 94 elements have been detected directly on Earth as primordial nuclides present from the formation of the solar system, or as naturally occurring fission or transmutation products of uranium and thorium. The remaining 24 heavier elements, not found today either on Earth or in astronomical spectra, have been produced artificially: Technetium was the first purportedly non-naturally occurring element synthesized, inalthough trace amounts of technetium have since been found in nature and also the element may have been discovered naturally in The nuclides of stable and radioactive elements are also available as a list of nuclidessorted by length of half-life for those that are unstable.
One of the most convenient, and certainly the most traditional presentation of the elements, is in the form of the periodic tablewhich groups together elements with similar chemical properties and usually also similar electronic structures.
Atomic number Main article: The electrons are placed into atomic orbitals that determine the atom's various chemical properties. The number of neutrons in a nucleus usually has very little effect on an element's chemical properties except in the case of hydrogen and deuterium.
Thus, all carbon isotopes have nearly identical chemical properties because they all have six protons and six electrons, even though carbon atoms may, for example, have 6 or 8 neutrons. That is why the atomic number, rather than mass number or atomic weightis considered the identifying characteristic of a chemical element.
The symbol for atomic number is Z. IsotopeStable isotope ratioand List of nuclides Isotopes are atoms of the same element that is, with the same number of protons in their atomic nucleusbut having different numbers of neutrons.
Thus, for example, there are three main isotopes of carbon. All carbon atoms have 6 protons in the nucleus, but they can have either 6, 7, or 8 neutrons. Since the mass numbers of these are 12, 13 and 14 respectively, the three isotopes of carbon are known as carboncarbonand carbonoften abbreviated to 12C, 13C, and 14C.
Carbon in everyday life and in chemistry is a mixture of 12C about Most 66 of 94 naturally occurring elements have more than one stable isotope.
Except for the isotopes of hydrogen which differ greatly from each other in relative mass—enough to cause chemical effectsthe isotopes of a given element are chemically nearly indistinguishable.
All of the elements have some isotopes that are radioactive radioisotopesalthough not all of these radioisotopes occur naturally.
The radioisotopes typically decay into other elements upon radiating an alpha or beta particle. If an element has isotopes that are not radioactive, these are termed "stable" isotopes.How radiometric dating works in general: Radioactive elements decay gradually into other elements.
The original element is called the parent, and the result of the decay process is . Carbon, 14 C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.
Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues () to date archaeological, geological and hydrogeological samples.
A radioactive atom can decay by emitting a beta particle which is a fast moving electron. A natural example of beta emission is the decay of carbon into nitrogen The equation for the decay is.
A chemical element is a species of atoms having the same number of protons in their atomic nuclei (that is, the same atomic number, or Z). For example, the atomic number of oxygen is 8, so the element oxygen consists of all atoms which have exactly 8 protons..
elements have been identified, of which the first 94 occur naturally on Earth with the remaining 24 being synthetic elements. The two general kinds of nuclear reactions are nuclear decay reactions and nuclear transmutation reactions.
For example, carbon undergoes beta decay to form nitrogen identify the type(s) of decay and write a balanced nuclear equation. Po → Pb +? Ir → Pt +? Am → 57 Fe + ? +? Here is a history of questions and answers processed by "Ask the Physicist!".
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