The Physics
Opus in profectus

Atomic Models

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  1. Write something.
  2. Write something.
  3. Write something.
  4. Write something completely different.


  1. Read this rather long passage.

    Physicists working in Europe announced yesterday that they had passed through nature's looking glass and had created atoms made of antimatter, or antiatoms, opening up the possibility of experiments in a realm once reserved for science fiction writers. Such experiments, theorists say, could test some of the basic tenets of modern physics and light the way to a deeper understanding of nature….

    By corralling clouds of antimatter particles in a cylindrical chamber laced with detectors and electric and magnetic fields, the physicists assembled antihydrogen atoms, the looking glass equivalent of hydrogen, the most simple atom in nature. Whereas hydrogen consists of a positively charged proton circled by a negatively charged electron, in antihydrogen the proton's counterpart, a positively charged antiproton, is circled by an antielectron, otherwise known as a positron….

    According to the standard theories of physics, the antimatter universe should look identical to our own. Antihydrogen and hydrogen atoms should have the same properties, emitting the exact same frequencies of light, for example….

    Antimatter has been part of physics since 1927 when its existence was predicted by the British physicist Paul Dirac. The antielectron, or positron, was discovered in 1932. According to the theory, matter can only be created in particle–antiparticle pairs. It is still a mystery, cosmologists say, why the universe seems to be overwhelmingly composed of normal matter.

    New York Times, 2002

    1. Which particle mentioned in the article has the charge incorrectly identified?
    2. How should the emission spectrum of antihydrogen compare to the emission spectrum of hydrogen?
    3. Identify one characteristic that antimatter particles must possess if clouds of them can be corralled by electric and magnetic fields.
    4. According to the article, why is it a mystery that "the universe seems to be overwhelmingly composed of normal matter"?


  1. A photon with a frequency of 5.02 × 1014 Hz is absorbed by an excited hydrogen atom. This causes the electron to be ejected from the atom, forming an ion.
    1. Calculate the energy of the photon in joules.
    2. Determine the energy of the photon in electron volts.
    3. What is the number of the lowest energy level (closest to the ground state) of a hydrogen atom that contains an electron that would be ejected by the absorption of this photon?
    4. What is the kinetic energy of the ejected electron in electron volts?
    5. What is the kinetic energy of the ejected electron in joules?
    6. How fast is the electron moving?
  2. In a mercury atom, as an electron moves from energy level i to energy level a, a single photon is emitted.
    1. Determine the emitted photon's energy.
    2. What kind of electromagnetic radiation is this?