CHEMISTRY GLOSSARY

Fermi level    →   Fermijev nivo

Fermi level is the highest energy of occupied states in a solid at zero temperature. The Fermi level in conductors lies in the conduction band, in insulators it lies in the valence band, and in semiconductors it falls in the gap between the conduction band and the valence band. It was named after the Italian physicst Enrico Fermi (1901 - 1954).

Lyman series    →   Lymanova serija

Lyman series is the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the ground state (principal quantum number n = 1) and successive excited states.

nuclear reactor    →   nuklearni reaktor

Nuclear reactor is an assembly of fissionable material (uranium-235 or plutonium-239) designed to produce a sustained and controllable chain reaction for the generation of electric power.

The essential components of a nuclear reactor are:

1. The core, metal rods containing enough fissionable material to maintain a chain reaction at the necessary power level (as much as 50 t of uranium may be required).
2. A source of neutrons to initiate the reaction (such as a mixture of polonium and beryllium)
3. A moderator to reduce the energy of fast neutrons for more efficient fission (material such as graphite, beryllium, heavy water, and light water are used)
4. A coolant to remove the fission-generated heat (water, sodium, helium, and nitrogen may be used)
5. A control system such as rods of boron or cadmium that have high capture cross sections (to absorb neutrons)
6. Adequate shielding, remote-control equipment, and appropriate instrumentation are essential for personnel safety and efficient operation.

Pauli exclusion principle    →   Paulijev princip zabrane

Pauli exclusion principle is the statement that two electrons in an atom cannot have identical all four quantum numbers. It was first formulated in 1925 by the Austrian-born Swiss physicst Wolfgang Ernst Pauli (1900-1958).

Paschen series    →   Paschenova serija

Paschen series are the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the state with principal quantum number n = 3 and successive higher states.

second    →   sekunda

Second (s) is the SI base unit of time.

The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels (F = 4, m_F = 0 to F = 3, m_F = 0) of the ground state of the caesium 133 atom.

Zeeman effect    →   Zeemanov efekt

Zeeman effect is the splitting of the lines in a spectrum when the source of the spectrum is exposed to a magnetic field. The effect was discovered in 1896 by the Dutch physicist Pieter Zeeman (1865-1943) as a broadening of the yellow D-lines of sodium in a flame held between strong magnetic poles.

The Zeeman effect has helped physicists determine the energy levels in atoms. In astronomy, the Zeeman effect is used in measuring the magnetic field of the Sun and of other stars.