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This website is also cited in the CRC Handbook as source of Section 1, subsection Electron Configuration of Neutral Atoms in the Ground State. 91 Pa : [Rn] 5f 2 (3 H 4) 6d 7s 2; 92 U : [Rn] 5f 3 (4 I o 9/2) 6d 7s 2; 93 Np : [Rn] 5f 4 (5 I 4) 6d 7s 2; 103 Lr : [Rn] 5f 14 7s 2 7p 1 question-marked; 104 Rf : [Rn] 5f 14 6d 2 7s 2 question-marked
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 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).
Fluorine atoms have nine electrons, one fewer than neon, and electron configuration 1s 2 2s 2 2p 5: two electrons in a filled inner shell and seven in an outer shell requiring one more to be filled. The outer electrons are ineffective at nuclear shielding , and experience a high effective nuclear charge of 9 − 2 = 7; this affects the atom's ...
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 Ne, 10, neon : 1s 2 2s 2 2p 6 Ar, 18, argon : 1s 2 2s 2 2p 6 3s 2 3p 6 Kr, 36, krypton : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 ...
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.
The lightest atom that requires the second rule to determine the ground state term is titanium (Ti, Z = 22) with electron configuration 1s 2 2s 2 2p 6 3s 2 3p 6 3d 2 4s 2. In this case the open shell is 3d 2 and the allowed terms include three singlets ( 1 S, 1 D, and 1 G) and two triplets ( 3 P and 3 F).
For Cr as an example the rule predicts the configuration 3d 4 4s 2, but the observed atomic spectra show that the real ground state is 3d 5 4s 1. To explain such exceptions, it is necessary to consider the effects of increasing nuclear charge on the orbital energies, as well as the electron–electron interactions including both Coulomb ...