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## The elementary particles

Atoms are made up of different elementary particles: the electrons (e^{-}), the protons (p^{+}) and the neutrons (n). They differ in charge and mass. The elementary charge is$\mathrm{1,6}\cdot {10}^{-19}$$\mathit{C.}$ (Coulomb). In the case of the charge of the elementary particles, however, only the integral multiple of this elementary charge is given (+ 1 / -1). The electrons are negatively charged and the protons are positive. Neutrons have no charge.

The rest mass of elementary particles and atoms is usually given in the atomic mass unit u. It corresponds to a twelfth of the mass of a carbon atom (exactly: ${}^{12}\text{C.}$-Isotope, see Isotopes).

Mass of a ${}^{12}\text{C.}$-Atoms = 12 u1 u = $\mathrm{1,666}\cdot {10}^{-24}\phantom{\rule{.2em}{0ex}}\text{G}$

Protons and neutrons are about 2000 times as heavy as electrons.

- Tab. 1

Elementary particles | symbol | charge | Mass (in $\text{G}$) | Mass (in u) |
---|---|---|---|---|

electron | e | -1 | $\mathrm{9,1}\cdot {10}^{-28}$ | 0,0005 |

proton | p | +1 | $\mathrm{1,6}\cdot {10}^{-24}$ | 1,0073 |

neutron | n | 0 | $\mathrm{1,6}\cdot {10}^{-24}$ | 1,0087 |