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Secondly, he found the charge-to-mass ratio of alpha particles to be half that of the hydrogen ion. Rutherford proposed three explanations: 1) an alpha particle is a hydrogen molecule (H 2) with a charge of 1 e; 2) an alpha particle is an atom of helium with a charge of 2 e; 3) an alpha particle is half a helium atom with a charge of 1 e.
Some disciplines use the charge-to-mass ratio (Q/m) instead, which is the multiplicative inverse of the mass-to-charge ratio. The CODATA recommended value for an electron is Q / m = −1.758 820 008 38 (55) × 10 11 C⋅kg −1 .
As such, the fine-structure constant is chiefly a quantity determining (or determined by) the elementary charge: e = √ 4πα ≈ 0.302 822 12 in terms of such a natural unit of charge. In the system of atomic units , which sets e = m e = ħ = 4 πε 0 = 1 , the expression for the fine-structure constant becomes α = 1 c . {\displaystyle ...
W-to-Z mass ratio: m W /m Z = 0.881 45 (13) u r (m W /m Z) = 1.5 × 10 −4 [71] malpha: alpha particle mass m α = 6.644 657 3450 (21) × 10 −27 kg: u r (m α) = 3.1 × 10 −10 [72] malpha_Da: alpha particle mass in daltons: m α = 4.001 506 179 129 (62) Da: u r (m α) = 1.6 × 10 −11 [73] malphac2_GeV: alpha particle ...
In 1908, Rutherford sought to independently determine the charge and mass of alpha particles. To do this, he wanted to count the number of alpha particles and measure their total charge; the ratio would give the charge of a single alpha particle.
In particle physics, the electron mass (symbol: m e) is the mass of a stationary electron, also known as the invariant mass of the electron. It is one of the fundamental constants of physics . It has a value of about 9.109 × 10 −31 kilograms or about 5.486 × 10 −4 daltons , which has an energy-equivalent of about 8.187 × 10 −14 joules ...
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It has a charge of +2 e and a mass of 4 Da. For example, uranium-238 decays to form thorium-234. While alpha particles have a charge +2 e, this is not usually shown because a nuclear equation describes a nuclear reaction without considering the electrons – a convention that does not imply that the nuclei necessarily occur in neutral atoms.