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The term nucleus is from the Latin word nucleus, a diminutive of nux ('nut'), meaning 'the kernel' (i.e., the 'small nut') inside a watery type of fruit (like a peach). In 1844, Michael Faraday used the term to refer to the "central point of an atom". The modern atomic meaning was proposed by Ernest Rutherford in 1912. [11]
In atomic physics, the effective nuclear charge of an electron in a multi-electron atom or ion is the number of elementary charges an electron experiences by the nucleus. It is denoted by Z eff . The term "effective" is used because the shielding effect of negatively charged electrons prevent higher energy electrons from experiencing the full ...
The atomic number or nuclear charge number (symbol Z) of a chemical element is the charge number of its atomic nucleus. For ordinary nuclei composed of protons and neutrons , this is equal to the proton number ( n p ) or the number of protons found in the nucleus of every atom of that element.
But the n=2 electrons see an effective charge of Z − 1, which is the value appropriate for the charge of the nucleus, when a single electron remains in the lowest Bohr orbit to screen the nuclear charge +Z, and lower it by −1 (due to the electron's negative charge screening the nuclear positive charge). The energy gained by an electron ...
However, a helium nucleus weighs less than the sum of the weights of the two heavy hydrogen nuclei which combine to make it. [6] The same is true for carbon, nitrogen and oxygen. For example, the carbon nucleus is slightly lighter than three helium nuclei, which can combine to make a carbon nucleus. This difference is known as the mass defect.
The rms charge radius is a measure of the size of an atomic nucleus, particularly the proton distribution. The proton radius is about one femtometre = 10 −15 metre. It can be measured by the scattering of electrons by the nucleus. Relative changes in the mean squared nuclear charge distribution can be precisely measured with atomic spectroscopy.
An up quark has electric charge + + 2 / 3 e, and a down quark has charge − + 1 / 3 e, so the summed electric charges of proton and neutron are +e and 0, respectively. [a] Thus, the neutron has a charge of 0 (zero), and therefore is electrically neutral; indeed, the term "neutron" comes from the fact that a neutron is ...
In that case, the charge of an ion could be written as =. The charge number in chemistry normally relates to an electric charge. This is a property of specific subatomic atoms. These elements define the electromagnetic contact between the two elements. A chemical charge can be found by using the periodic table.