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Orbitals and Bonding
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals. Electrons are distributed in shells, each of which has different types of electrons: s, p, d, f. Each orbital (energy level) occurs further from the nucleus; the electrons are held less tightly. Each orbital can hold a maximum of two electrons and each energy level will contain different numbers of electrons (one electron for the 1s1 and two electrons for the 1s2 orbital, as shown. There are six electrons for p-orbitals; two each is possible for each of the three-degenerate p-orbitals. There are ten electrons for d-orbitals; two each for the five d-orbitals. Orbitals will fill from lowest energy to highest energy orbital, according to the order shown in the mnemonic for the electronic filling order of orbitals.
Spectroscopy and Atomic Physics
Published in M.B. Hooper, Laser-Plasma Interactions 4, 2020
A multi-charged ion can be visualized as a point nucleus of infinite mass and charge Z surrounded by N electrons. The various electrons are classified under so-called shells of electrons. All electrons belonging to the same shell have the same principal quantum number n. One may ascribe to each electron a set of quantum numbers: 1, the azimuthal quantum number (lmax=n−l), ml the magnetic quantum number (-1<m1<1) and mS=±1/2 the spin quantum number. The Pauli exclusion principle requires all individual sets to be distinct. The states of an electron which are characterized by certain values of n and 1 are called orbitals. Electrons belonging to the same orbital are called equivalent electrons. The complete distribution of electrons among the orbitals is called an electron configuration. If the potential seen by the outer electrons was purely hydrogenic, stable elements would correspond to filled shells with 2(He-like), 10(Ne-like), 28(Ni-like),... electrons. In reality, it is well known that this is not the case for neutral atoms. However, for high charge ions, the nuclear potential is increasingly important relative to the inter-electron contribution and the filling of orbitals follows essentially hydrogenic order. This fact, recently noted by More(2), explains the predominence of nickel-like ion emissions in the 2-4 keV range for elements with Z > 50. A recent review on atomic structure and spectral emissions in highly-ionized atoms can be found in Ref 3.
Metal–ring interactions in actinide sandwich compounds: A combined normalized elimination of the small component and local vibrational mode study
Published in Molecular Physics, 2020
Małgorzata Z. Makoś, Wenli Zou, Marek Freindorf, Elfi Kraka
In order to describe the role of 5f electrons in An-ring bonding, the 5f orbital occupation number of the An atom of each compound investigated in this work was calculated via an NBO analysis and compared with the corresponding local stretching force constant (An-M). In Table 1 all 5f occupation numbers are collected. In Figure 6, the 5f occupation numbers are compared with the local stretching force constants (An-M). An isolated Th atom with the electron configuration of has no 5 f occupation. This is reflected by the close to zero values in Table 1 found for all Th sandwich complexes, independent of the type and size of the ring. However, as depicted in Figure 6 the local (An-M) force constants vary from 2.361 mDyn/Å(6MR) to 3.584 mDyn/Å(8MR), showing a clear variation in metal–ring bonding. This indicates that 5f molecular orbitals do not participate in the Th-ring interaction, in line with the finding that Th tends to resemble d-block transition metals [160,161]. The 5f occupation numbers of the Pa complexes are in the range of 1.18 e (5MR)–1.73 e (8MR), being smaller than the 5f occupation number in the isolated Pa atom (). However, there is no direct correlation with the local stretching force constants (Pa-M), i.e. the interaction is not dominated by 5f electron participation.
Novel cis-[PdCl2(NHC)(PPh3)] complex: synthesis, crystal structure, spectral investigations, DFT and NCI studies, prediction of biological activity
Published in Journal of Coordination Chemistry, 2020
The atomic charge distributions for the complex were calculated with theB3LYP/LanL2DZ//6–31G* basis set. Charges of atoms were calculated from natural population analysis (NPA). Normally, the electron configuration of free Pd atom with +2 charge is [core]4d8. However, in this study, the atomic charge of the molecule shows that the electron number of Pd1 5 s, 4d, 5p and 5d orbits are 0.42, 9.13, 0.55 and 0.01, respectively, while the net charge is −0.09663 (Table 5). This discrepancy can be indicated by the electron charge transfer from ligand to metal. The electron numbers of 5p and 5d are smaller, so it can be concluded that the Pd atom coordination with Cl1, Cl2, P1, and C1 atoms are mainly on 4d orbit. The chloride atoms provide an electron of 3s (1.89) and 3p (5.55) to palladium, to form the coordination bonds. The P1 is the most positive atom in the complex, owing to its connection to the most electronegative carbon atoms C16, C22, C28, and Pd metal.
New modified-majority voter-based efficient QCA digital logic design
Published in International Journal of Electronics, 2019
Ali Newaz Bahar, Firdous Ahmad, Shahjahan Wani, Safina Al-Nisa, Ghulam Mohiuddin Bhat
QCA cell is the basic unit of any circuit design as shown in Figure 1. Each cell consists of four quantum dots positioned at each corner of a quantum cell. Two electrons are loaded at antipodal sides. An electron configuration exists in a quantum dot due to Coulombic interactions. The state of QCA cell is represented by its polarisations denoted as P = + 1 and P = –1 and is symbolised by binary values of ‘binary 1’ and ‘binary 0’ (Lent et al., 1993; Tougaw & Lent, 1994).