The negative electrons are attracted to the positive nucleus by an electrical force. This is how the atom stays together. It is the number of protons in the nucleus the atomic number that distinguishes each element. The number of protons is unique to each element. For example, there are six protons in carbon; therefore, its atomic number is 6 on the periodic table.
Atoms are stable when the number of neutrons and protons in the nucleus are balanced. When there is a significant imbalance between the number of neutrons and protons in a nucleus, the atom becomes unstable and in order to achieve stability, the atom may undergo a transformation or radioactive decay. Atoms from one or more elements combine to form larger compounds, which are called molecules.
A molecule of water, for example, is formed of two atoms of hydrogen combined with one atom of oxygen H 2 O. A nuclide is a specific type of atom characterized by the number of protons and neutrons in the nucleus, which approximates the mass of the nuclide.
The number that is sometimes given with the name of the nuclide is called its mass number the total number of protons and neutrons in the nucleus. For example, carbon is a nuclide of carbon with 6 protons and 6 neutrons. Nuclides of an element that have the same number of protons but not the same number of neutrons are called isotopes of that element.
They are a variant of a basic element. For example, there are three isotopes or variants of hydrogen: hydrogen-1 one proton and no neutrons , hydrogen-2 or deuterium one proton and one neutron , and hydrogen-3 which is called tritium one proton and two neutrons. Another example is uranium which has 92 protons and neutrons, and uranium which has 92 protons and neutrons.
Both uranium and uranium are isotopes of uranium. Many isotopes are stable. They will not undergo radioactive decay and give off radiation.
Other isotopes are not stable. Natural Uranium is made up of While U usually stays together in a neutron field, U readily splits, or fissions, in the presence of neutrons, releasing huge amounts of energy.
This energy runs nuclear reactors and nuclear weapons alike. To create a chain reaction, you must enrich natural Uranium to contain more U A typical nuclear reactor requires about 3. See figure below. Enrichment is a very difficult process, as the mass difference between each isotope is minuscule. The newsworthy item about it is that anyone who can enrich can create highly-enriched uranium, a good material with which to make nuclear weapons. Countries that want to have their own nuclear fuel manufacturing capabilities argue that they need enrichment plants, but opponents argue that they are just looking to produce nuclear weapons.
Isotope and nuclide are closely related terms. When one speaks of isotopes, they are referring to the set of nuclides that have the same number of protons. Nuclide is a more general term, referring to a nuclear species that may or may not be isotopes of a single element. Some elements have unstable radioactive isotopes, either because their decay is so slow that a fraction still remains since they were created examples: uranium, potassium , or because they are continually created through cosmic radiation tritium, carbon or by decay from an isotope in the first category radium, radon.
The tabulated atomic masses of elements are averages that account for the presence of multiple isotopes with different masses. A good example is chlorine , having the composition 35 Cl, Values like this confounded scientists before the discovery of isotopes, as most light element atomic masses are close to integer multiples of hydrogen.
According to generally accepted cosmology only the isotopes of hydrogen and helium, and traces of some isotopes of lithium, beryllium and boron were created at the big bang, while all others were synthesized in stars and supernovae. See nucleosynthesis. Their respective abundances on Earth result from the quantities formed by these processes, their spread through the galaxy, and their rates of decay. After the initial coalescence of the solar system, isotopes were redistributed according to mass, and the isotopic composition of elements varies slightly from planet to planet.
This sometimes makes it possible to trace the origin of meteorites. The molecular mass M r of an element is determined by its nucleons. For example, Carbon 12 C has 6 Protons and 6 Neutrons.
Several applications exist that capitalize on properties of the various isotopes of a given element. Template:WikiDoc Sources. In the bottom right corner of JJ Thomson's photographic plate are markings for the two isotopes of neon: neon and neon Mass spectrometry reviews.
PMID Jamin et al. Food Chem. Treiman, J.
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