Atom: summary (brief resume)

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  • The atom can be defined as the structure through which matter is placed;
  • Sets of atoms are called molecules;
  • Atoms can be made up of protons, neutrons, electrons;
  • Protons have a positive charge;
  • Neutrons don’t have a charge;
  • Electrons have a negative charge;
  • The atom was theorized in part, as a smaller and non-divisible part of matter, by some philosophers of ancient Greece, including Democritus, Epicurus, Leucippus;
  • The atom is divisible (as will be demonstrated in the nineteenth century) in the subatomic particles of which it is composed;
  • The structure of the atom is, therefore, that of a nucleus of protons and neutrons, surrounded by electrons;
  • The four types of interaction that the atom is subjected to are gravitational interaction, strong interaction, weak interaction, gravitational interaction;

  • John Dalton was the first to reformulate Democritus theory and elaborate modern atomic theory;
  • Joseph John Thomson elaborated in 1902 the first physical model of the atom, with the panettone model (“plum pudding model”);
  • Ernest Rutherford in 1910, together with Geiger and Marsden, developed the theory of the atomic planetary model and the theory of collapse;
  • Niels Bohr in 1913 introduces the Bohr model;
  • Werner Karl Heisenberg in 1927 establishes the uncertainty principle;
  • The neutron was discovered in 1932; Protons (having a positive charge) and neutrons (which have no charge) are called “nucleons” and form the nucleus of the atom;
  • The electrons (which have a negative charge) are equal to the number of protons and are delocalized, that is, they are not characterized by a determined orbit but still remain within energy levels, called “orbitals”.
  • When protons and electrons are present in different numbers in the atom, the atom itself is called “ion” and has an imbalance in the charge, that is, it will be charged positively or negatively, but it will not be neutral.
  • Unstable atoms may also exist where sub-atomic particles are replaced by different particles with the same charge. These atoms are called “exotic atoms” and are highly unstable, as in the case of the mesic atom;
  • Protons are subject to a force that prevents them from detaching, despite having the same charge, this force is called “strong nuclear force”;

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