explain electronic configuration

Asked by  | 9th Jun, 2008, 05:06: PM

Expert Answer:

  1. In atomic physics and quantum chemistry, electron configuration is the arrangement of electrons in an atom, molecule, or other physical structure. Like other elementary particles the electron is subject to the laws of quantum mechanics, and exhibits both particle-like and wave-like nature. Knowledge of the electron configuration of different atoms is useful in understanding the structure of the periodic table of elementsThe state of an electron in an atom is given by four quantum numbers. Three of these are integers and are properties of the atomic orbital in which it sits.No two electrons in one atom can have the same set of these four quantum numbers (Pauli exclusion principle).
  2. Shells and subshells (also called energy levels and sublevels) are defined by the quantum numbers, not by the distance of its electrons from the nucleus, or even their overall energy. In large atoms, shells above the second shell overlap (see Aufbau principle).

    States with the same value of n are related, and said to lie within the same electron shell.
    States with the same value of n and also l are said to lie within the same electron subshell, and those electrons having the same n and l are called equivalent electrons.
    If the states also share the same value of m, they are said to lie in the same atomic orbital.
    Because electrons have only two possible spin states, an atomic orbital cannot contain more than two electrons (Pauli exclusion principle).

    A subshell can contain up to 4l + 2 electrons; a shell can contain up to 2n2 electrons; where n equals the shell number.

    Physicists and chemists use a standard notation to describe atomic electron configurations. In this notation, a subshell is written in the form nxy, where n is the shell number, x is the subshell label and y is the number of electrons in the subshell. An atom's subshells are written in order of increasing energy – in other words, the sequence in which they are filled (see Aufbau principle below).

    For instance, ground-state hydrogen has one electron in the s orbital of the first shell, so its configuration is written 1s1. Lithium has two electrons in the 1s subshell and one in the (higher-energy) 2s subshell, so its ground-state configuration is written 1s2 2s1. Phosphorus (atomic number 15), is as follows: 1s2 2s2 2p6 3s2 3p3.

Answered by  | 11th Jun, 2008, 03:40: AM

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