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  2. History of atomic theory - Wikipedia

    en.wikipedia.org/wiki/History_of_atomic_theory

    The current theoretical model of the atom involves a dense nucleus surrounded by a probabilistic "cloud" of electrons. Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years in response to scientific discoveries.

  3. Half-life - Wikipedia

    en.wikipedia.org/wiki/Half-life

    Half-life (symbol t ½) is the time required for a quantity (of substance) to reduce to half of its initial value.The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive.

  4. Azimuthal quantum number - Wikipedia

    en.wikipedia.org/wiki/Azimuthal_quantum_number

    The azimuthal quantum number was carried over from the Bohr model of the atom, and was posited by Arnold Sommerfeld. [11] The Bohr model was derived from spectroscopic analysis of atoms in combination with the Rutherford atomic model. The lowest quantum level was found to have an angular momentum of zero.

  5. Nuclear transmutation - Wikipedia

    en.wikipedia.org/wiki/Nuclear_transmutation

    The term transmutation dates back to alchemy.Alchemists pursued the philosopher's stone, capable of chrysopoeia – the transformation of base metals into gold. [3] While alchemists often understood chrysopoeia as a metaphor for a mystical or religious process, some practitioners adopted a literal interpretation and tried to make gold through physical experimentation.

  6. Atomic electron transition - Wikipedia

    en.wikipedia.org/wiki/Atomic_electron_transition

    The energy of an electron is determined by its orbit around the atom, The n = 0 orbit, commonly referred to as the ground state, has the lowest energy of all states in the system. In atomic physics and chemistry , an atomic electron transition (also called an atomic transition, quantum jump, or quantum leap) is an electron changing from one ...

  7. Proton-to-electron mass ratio - Wikipedia

    en.wikipedia.org/wiki/Proton-to-electron_mass_ratio

    Astrophysicists have tried to find evidence that μ has changed over the history of the universe. (The same question has also been asked of the fine-structure constant.) One interesting cause of such change would be change over time in the strength of the strong force.

  8. Radioactive decay - Wikipedia

    en.wikipedia.org/wiki/Radioactive_decay

    the equation indicates that the decay constant λ has units of t −1, and can thus also be represented as 1/ τ, where τ is a characteristic time of the process called the time constant. In a radioactive decay process, this time constant is also the mean lifetime for decaying atoms.

  9. Rydberg formula - Wikipedia

    en.wikipedia.org/wiki/Rydberg_formula

    Examples would include He +, Li 2+, Be 3+ etc., where no other electrons exist in the atom. But the Rydberg formula also provides correct wavelengths for distant electrons, where the effective nuclear charge can be estimated as the same as that for hydrogen, since all but one of the nuclear charges have been screened by other electrons, and the ...