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1. A reminder of the structure of matter
1.1 Atom
Atoms are made up of elementary particles: protons and neutrons combined in a very dense nucleus carrying a positive electric charge, and electrons, very light negatively-charged particles in motion around the nucleus.
Atoms have a total radius of the order of 0.1 nm, and atomic nuclei have dimensions of the order of a few femtometers (10 –15 m). Electrons, on the other hand, are point particles with no dimensions. The mass of a proton or neutron is approximately 1.7 × 10 – 27 kg, that of an electron 9.1 × 10 – 31 kg.
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A reminder of the structure of matter
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