Hydrogen atom Hydrogen atom A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively charged proton and a single negatively charged electron bound to the nucleus by the Coulomb force. Atomic hydrogen constitutes about 75% of the baryonic mass of the universe. In everyday life on Earth, isolated hydrogen atoms (called "atomic hydrogen") are extremely rare. Instead, hydrogen tends to combine with other atoms in compounds, or with itself to form ordinary (diatomic) hydrogen gas, H. "Atomic hydrogen" and "hydrogen atom" in ordinary English use have overlapping, yet distinct, meanings. For example, a
Vector model of the atom The process of adding all angular momenta together is a laborious task, since the resultant momenta is not definite, the entire cones of precessing momenta about the z-axis must be incorporated into the calculation. This can be simplified by some developed approximations - such as the "Russell-Saunders coupling" scheme in L-S coupling, named after H. N. Russell and F. A. Saunders (1925). Vector model of the atom In physics, in particular quantum mechanics, the vector model of the atom is a model of the atom in terms of angular momentum. It can be considered as the extension of the Rutherford-Bohr-Sommerfeld