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The ions with the largest number of unpaired electrons are Gd 3+ and Cm 3+ with seven unpaired electrons. An unpaired electron has a magnetic dipole moment, while an electron pair has no dipole moment because the two electrons have opposite spins so their magnetic dipole fields are in opposite directions and cancel. Thus an atom with unpaired ...
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.
The highest occupied orbital energy level of dioxygen is a pair of antibonding π* orbitals. In the ground state of dioxygen, this energy level is occupied by two electrons of the same spin, as shown in the molecular orbital diagram. The molecule, therefore, has two unpaired electrons and is in a triplet state.
As a result, when filling up atomic orbitals, the maximum number of unpaired electrons (and hence maximum total spin state) is assured. The valence orbitals of the oxygen atom (sides of diagram) and the dioxygen molecule (middle) in the ground state. In both atom and molecule, the electrons in singly occupied orbitals have their spins parallel.
For example, the electron configuration of the neon atom is 1s 2 2s 2 2p 6, meaning that the 1s, 2s, and 2p subshells are occupied by two, two, and six electrons, respectively. Electronic configurations describe each electron as moving independently in an orbital , in an average field created by the nuclei and all the other electrons.
The maximum number of unpaired electrons is 7, in Gd 3+, with a magnetic moment of 7.94 B.M., but the largest magnetic moments, at 10.4–10.7 B.M., are exhibited by Dy 3+ and Ho 3+. However, in Gd 3+ all the electrons have parallel spin and this property is important for the use of gadolinium complexes as contrast reagent in MRI scans.
The filled MO highest in energy is called the highest occupied molecular orbital (HOMO) and the empty MO just above it is then the lowest unoccupied molecular orbital (LUMO). The electrons in the bonding MO's are called bonding electrons and any electrons in the antibonding orbital would be called antibonding electrons. The reduction in energy ...
An electron state has spin number s = 1 / 2 , consequently m s will be + 1 / 2 ("spin up") or - 1 / 2 "spin down" states. Since electron are fermions they obey the Pauli exclusion principle: each electron state must have different quantum numbers. Therefore, every orbital will be occupied with at most two electrons, one ...