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in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. [13] Electrons belong to the first generation of the lepton particle family, [14] and are generally thought to be elementary particles because they have no known components or substructure. [1] The electron's mass is approximately 1/1836 that of the ...
The negatively charged electron has a mass of about 1 / 1836 of that of a hydrogen atom. The remainder of the hydrogen atom's mass comes from the positively charged proton. The atomic number of an element is the number of protons in its nucleus. Neutrons are neutral particles having a mass slightly greater than that of the proton.
A proton is a stable subatomic particle, symbol. p. , H +, or 1 H + with a positive electric charge of +1 e (elementary charge). Its mass is slightly less than the mass of a neutron and approximately 1836 times the mass of an electron (the proton-to-electron mass ratio). Protons and neutrons, each with a mass of approximately one atomic mass ...
The total number of these particles (called "nucleons") in a given atom is called the mass number. It is a positive integer and dimensionless (instead of having dimension of mass), because it expresses a count. An example of use of a mass number is "carbon-12," which has 12 nucleons (six protons and six neutrons).
In the 1911 Rutherford model, the atom consisted of a small positively charged massive nucleus surrounded by a much larger cloud of negatively charged electrons. In 1920, Ernest Rutherford suggested that the nucleus consisted of positive protons and neutrally charged particles, suggested to be a proton and an electron bound in some way. [46]
The magnitude of this charge is proportional to (up to a charge number that can be approximately half of) the atom's atomic mass—the remaining mass is now known to be mostly attributed to neutrons. This concentrated central mass and charge is responsible for deflecting both alpha and beta particles.
A hypothetical atom with seven electrons, arranged in a pentagonal dipyramid, as imagined by Thomson in 1905. The plum pudding model was the first scientific model of the atom with internal structure. It was first proposed by J. J. Thomson in 1904 following his discovery of the electron in 1897, but it was subsequently rendered obsolete by ...
Electric charge is a conserved property: the net charge of an isolated system, the quantity of positive charge minus the amount of negative charge, cannot change. Electric charge is carried by subatomic particles. In ordinary matter, negative charge is carried by electrons, and positive charge is carried by the protons in the nuclei of atoms.