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The configuration that corresponds to the lowest electronic energy is called the ground state. Any other configuration is an excited state. As an example, the ground state configuration of the sodium atom is 1s 2 2s 2 2p 6 3s 1, as deduced from the Aufbau principle (see below).
CRC Press. Boca Raton, Florida, 2003; Section 1, Basic Constants, Units, and Conversion Factors; Electron Configuration of Neutral Atoms in the Ground State. (elements 1–104) Also subsection Periodic Table of the Elements, (elements 1–103) based on:
Energy levels for an electron in an atom: ground state and excited states. After absorbing energy, an electron may jump from the ground state to a higher-energy excited state. The ground state of a quantum-mechanical system is its stationary state of lowest energy; the energy of the ground state is known as the zero-point energy of the system.
As an example, consider the ground state of silicon.The electron configuration of Si is 1s 2 2s 2 2p 6 3s 2 3p 2 (see spectroscopic notation).We need to consider only the outer 3p 2 electrons, for which it can be shown (see term symbols) that the possible terms allowed by the Pauli exclusion principle are 1 D , 3 P , and 1 S.
The rule then predicts the electron configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 9 4s 2, abbreviated [Ar] 3d 9 4s 2 where [Ar] denotes the configuration of argon, the preceding noble gas. However, the measured electron configuration of the copper atom is [Ar] 3d 10 4s 1. By filling the 3d subshell, copper can be in a lower energy state.
Configurations of elements 109 and above are not available. Predictions from reliable sources have been used for these elements. Grayed out electron numbers indicate subshells filled to their maximum. Bracketed noble gas symbols on the left represent inner configurations that are the same in each period. Written out, these are: He, 2, helium : 1s 2
Neutral atoms of the chemical elements have the same term symbol for each column in the s-block and p-block elements, but differ in d-block and f-block elements where the ground-state electron configuration changes within a column, where exceptions to Hund's rules occur. Ground state term symbols for the chemical elements are given below.
The manganese (Mn) atom has a 3d 5 electron configuration with five unpaired electrons all of parallel spin, corresponding to a 6 S ground state. [4] The superscript 6 is the value of the multiplicity , corresponding to five unpaired electrons with parallel spin in accordance with Hund's rule.