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  2. Helium atom - Wikipedia

    en.wikipedia.org/wiki/Helium_atom

    A helium atom is an atom of the chemical element helium. ... A state with the quantum numbers: principal quantum number , total spin , angular ...

  3. Helium - Wikipedia

    en.wikipedia.org/wiki/Helium

    At rates of use at that time (72 million SCM per year in the U.S.; see pie chart below) this would have been enough helium for about 58 years of U.S. use, and less than this (perhaps 80% of the time) at world use rates, although factors in saving and processing impact effective reserve numbers. Helium is generally extracted from natural gas ...

  4. Quantum number - Wikipedia

    en.wikipedia.org/wiki/Quantum_number

    A quantum number beginning in n = 3,ℓ = 0, describes an electron in the s orbital of the third electron shell of an atom. In chemistry, this quantum number is very important, since it specifies the shape of an atomic orbital and strongly influences chemical bonds and bond angles. The azimuthal quantum number can also denote the number of ...

  5. Hund's rules - Wikipedia

    en.wikipedia.org/wiki/Hund's_rules

    Hund's first rule states that the lowest energy atomic state is the one that maximizes the total spin quantum number for the electrons in the open subshell. The orbitals of the subshell are each occupied singly with electrons of parallel spin before double occupation occurs.

  6. Block (periodic table) - Wikipedia

    en.wikipedia.org/wiki/Block_(periodic_table)

    The s-block, with the s standing for "sharp" and azimuthal quantum number 0, is on the left side of the conventional periodic table and is composed of elements from the first two columns plus one element in the rightmost column, the nonmetals hydrogen and helium and the alkali metals (in group 1) and alkaline earth metals (group 2).

  7. Spectroscopic notation - Wikipedia

    en.wikipedia.org/wiki/Spectroscopic_notation

    This notation is used to specify electron configurations and to create the term symbol for the electron states in a multi-electron atom. When writing a term symbol, the above scheme for a single electron's orbital quantum number is applied to the total orbital angular momentum associated to an electron state.

  8. Term symbol - Wikipedia

    en.wikipedia.org/wiki/Term_symbol

    In atomic physics, a term symbol is an abbreviated description of the total spin and orbital angular momentum quantum numbers of the electrons in a multi-electron atom.So while the word symbol suggests otherwise, it represents an actual value of a physical quantity.

  9. Principal quantum number - Wikipedia

    en.wikipedia.org/wiki/Principal_quantum_number

    The four quantum numbers n, ℓ, m, and s specify the complete and unique quantum state of a single electron in an atom, called its wave function or orbital. Two electrons belonging to the same atom cannot have the same values for all four quantum numbers, due to the Pauli exclusion principle .