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 Glossaire
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| RÉDACTEURS: |
 AnglaisAditya Vardhan Eni Generalic |
 FrançaisMichel Ditria |
 CroateEni Generalic Marija Bralic Slobodan Brinic |
 AllemandMarc Hens |
 Italienrédacteurs recherchés |
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P |
Period | Periodic table of the elements | Permittivity | pH | Proton |
- Period
- Periods are characterized by the number of energy levels (shells) of electrons surrounding the nucleus. Elements in first period has only one shell and have a 2 electrons maximum (hydrogen has 1 electron and helium has 2 electrons), elements in second period has two shell and have a 10 electrons maximum, etc.
- Periodic table of the elements
- Periodic Table is an arrangement of elements in a geometric pattern designed to represent the periodic law by aligning elements into periods and groups. Elements with the same number of orbitals are in the same period and elements with the same number of electrons in the filling orbital and have other similar properties are in the same group.
- Permittivity
- Permittivity (e) is ratio of the electric displacement in a medium to the electric field strength. Also called dielectric constant.
- pH
- pH is a convenient measure of the acid-base character of a solution, usually defined by
pH = - log[H+] where c(H+) is the concentration of hydrogen ions. The more precise definition is in terms af activity (a) rather than concentration. Pure water has a pH of 7. Substances with a pH less than 7 are acids and substances with a pH greater than 7 are bases.
- Proton
- Proton is a stable elementary particle of unit positive charge and spin 1/2. Protons and neutrons are the constituents of the nucleus. Mass of a proton (mp) is 1.672 × 10-27 kg.
