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  2. Nuclear structure - Wikipedia

    en.wikipedia.org/wiki/Nuclear_structure

    The liquid drop model is one of the first models of nuclear structure, proposed by Carl Friedrich von Weizsäcker in 1935. [5] It describes the nucleus as a semiclassical fluid made up of neutrons and protons , with an internal repulsive electrostatic force proportional to the number of protons.

  3. Slater's rules - Wikipedia

    en.wikipedia.org/wiki/Slater's_rules

    An example provided in Slater's original paper is for the iron atom which has nuclear charge 26 and electronic configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2.The screening constant, and subsequently the shielded (or effective) nuclear charge for each electron is deduced as: [1]

  4. Aufbau principle - Wikipedia

    en.wikipedia.org/wiki/Aufbau_principle

    In atomic physics and quantum chemistry, the Aufbau principle (/ ˈ aʊ f b aʊ /, from German: Aufbauprinzip, lit. 'building-up principle'), also called the Aufbau rule, states that in the ground state of an atom or ion, electrons first fill subshells of the lowest available energy, then fill subshells of higher energy.

  5. Bohr–Sommerfeld model - Wikipedia

    en.wikipedia.org/wiki/Bohr–Sommerfeld_model

    This was a significant step in the development of quantum mechanics. It also described the possibility of atomic energy levels being split by a magnetic field (called the Zeeman effect). Walther Kossel worked with Bohr and Sommerfeld on the Bohr–Sommerfeld model of the atom introducing two electrons in the first shell and eight in the second. [8]

  6. Atomic nucleus - Wikipedia

    en.wikipedia.org/wiki/Atomic_nucleus

    The modern atomic meaning was proposed by Ernest Rutherford in 1912. [11] The adoption of the term "nucleus" to atomic theory, however, was not immediate. In 1916, for example, Gilbert N. Lewis stated, in his famous article The Atom and the Molecule , that "the atom is composed of the kernel and an outer atom or shell. " [ 12 ] Similarly, the ...

  7. Rutherford model - Wikipedia

    en.wikipedia.org/wiki/Rutherford_model

    In a May 1911 paper, [8] Rutherford presented his own physical model for subatomic structure, as an interpretation for the unexpected experimental results. [3] In it, the atom is made up of a central charge (this is the modern atomic nucleus, though Rutherford did not use the term "nucleus" in his paper). Rutherford only committed himself to a ...

  8. Atom - Wikipedia

    en.wikipedia.org/wiki/Atom

    A given atom has an atomic mass approximately equal (within 1%) to its mass number times the atomic mass unit (for example the mass of a nitrogen-14 is roughly 14 Da), but this number will not be exactly an integer except (by definition) in the case of carbon-12. [67] The heaviest stable atom is lead-208, [59] with a mass of 207.976 6521 Da. [68]

  9. Mass number - Wikipedia

    en.wikipedia.org/wiki/Mass_number

    The mass number (symbol A, from the German word: Atomgewicht, "atomic weight"), [1] also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approximately equal to the atomic (also known as isotopic) mass of the atom expressed in atomic mass units.