CHEMISTRY GLOSSARY

valence electron    →   valentni elektron

Valence electrons are electrons that can be actively involved in a chemical change, usually electrons in the outermost (valent) shell. For example, sodium’s ground state electron configuration is 1s² 2s² 2p⁶ 3s¹; the 3s electron is the only valence electron in the atom. Germanium (Ge) has the ground state electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p²; the 4s and 4p electrons are the valence electrons.

van der Waals’ equation    →   van der Waalsova jednadžba

Van der Waals’ equation is an equation of state for real fluids which takes the form:

where p is pressure, V_m is molar volume, T is temperature, R is the molar gas constant, and a and b are characteristic parameters of the substance which describe the effect of attractive and repulsive intermolecular forces.

zwitterion    →   dipolarni ion

Zwitterion, also known as inner salt or dipolar ion, is an ion with a positive and a negative electrical charge at different locations within a molecule. As the molecule contains two opposite charges, it is electrically neutral. The term zwitterion is derived from the German word zwitter, meaning a hybrid, hermaphrodite. Zwitterions can be formed from compounds that contain both acid groups and base groups in their molecules (ampholytes).

All of the common amino acids found in proteins are ampholytes because they contain a carboxyl group (-COOH) that acts as an acid and an amino group (-NH₂) that acts as a base. In the solid state, amino acids exist in the dipolar or zwitterion form. If acid is added to a solution containing the zwitterion, the carboxylate group captures a hydrogen (H⁺) ion, and the amino acid becomes positively charged. If base is added, ion removal of the H⁺ ion from the amino group of the zwitterion produces a negatively charged amino acid.