Changes

As stated above, an alpha particle is the nucleus of a Helium atom, i.e., two protons and two neutrons. This arrangement means the alpha particle has a charge of +2, and an atomic mass of 4, the symbol for which is <math>{{}_2^4}He^{+2}</math>.

As stated above, an alpha particle is the nucleus of a Helium atom, i.e., two protons and two neutrons. This arrangement means the alpha particle has a charge of +2, and an atomic mass of 4, the symbol for which is <math>{{}_2^4}He^{+2}</math>.

For example, the most common [[isotope]] of Uranium is Uranium-238. The [[mass number]]<ref>The mass number is the (integer) number of nucleons. It is very close to the [[atomic mass]] of the isotope measured in amu, because the masses of protons and neutrons are very close, and the deviations (due to [[E%3Dmc²]] are small. So the terms are often used nearly interchangeably.</ref>, 238, is the sum of the number of protons and the number of neutrons. Since all Uranium atoms have 92 protons, there are 146 neutrons. The initial step in Uranium-238 decaying (eventually) into Lead-206 is an alpha decay:

For example, the most common [[isotope]] of Uranium is Uranium-238. The [[mass number]]<ref>The mass number is the (integer) number of nucleons. It is very close to the [[atomic mass]] of the isotope measured in amu, because the masses of protons and neutrons are very close, and the deviations (due to [[E%3Dmc²]]) are small. So the terms are often used nearly interchangeably.</ref>, 238, is the sum of the number of protons and the number of neutrons. Since all Uranium atoms have 92 protons, there are 146 neutrons. The initial step in Uranium-238 decaying (eventually) into Lead-206 is an alpha decay:

<center><math>{{}_{92}^{238}}U </math> &rarr; <math>{{}_2^4}He + {{}_{90}^{234}}Th</math></center>

<center><math>{{}_{92}^{238}}U </math> &rarr; <math>{{}_2^4}He + {{}_{90}^{234}}Th</math></center>