The carbides (in which C reacts with another element to form a binary compound) can be broadly categorized depending on the nature of the bonding which exists within these compounds. Saline Carbides are those where the bonding is largely ionic; and Metallic Carbides are those which exhibit metallic conductivity. Saline Carbides These can be further subdivided into graphite intercalation compounds, dicarbides, … Read more
Carbon has electronic configuration [He]2s22p2, and main formal oxidation state +4 (there are other oxidation states, but all use all of carbon’s valence electrons in bonding). Alongside the central role of Carbon in Organic Chemistry, it forms numerous compounds, both inorganic and organometallic. There are two main isotopes, with relative abundances: 12C (98.9%, I=0), and 13C (1.1%, I=0.5). I is the nuclear … Read more
Preparation: BX3 are all planar monomeric species due to the extra B(pπ)-X(pπ) bonding (compare AlCl3, which dimerizes to give Al2Cl6, as the inter-molecular Lewis acid–Lewis base bonds are stronger than the intra-molecular bonds in BX3).Structure: Reactions: All BX3 are Lewis acids, with acid strength BF3<BCl3<BBr3<BI3.This reflects the loss of pπ-bonding when the BX3 distorts from planar to pyramidal on reaction with … Read more
Many boron hydrides, BnHm, are known, and the most important is diborane, B2H6. All are endothermic in formation, and have a formal boron oxidation state of less than three: some contain B-B bonds. They are reducing, acting by hydride (H–) ion transfer. Diborane B2H6: Preparation: Structure: Each B atom is tetrahedrally coordinated by H atoms. The central B-H-B bonds (the bridging bonds) are 3-centered, 2-electron … Read more
Boron has electronic configuration [He]2s22p1, and main formal oxidation state +3. Its bonding is mainly covalent, and it forms compounds with three bonds, and therefore six electrons in its valence shell: It is electron deficient. The bonding orbitals are sp2 hybrid orbitals, and the remaining p-orbital on B acts as a pi-acceptor orbital, eg. in BF3 , where the back donation … Read more
The interaction between the spin angular momentum quantum numbers of two electrons gives rise to states of so called different spin multiplicity, such as singlet and doublet states. The spin angular momentum of an electron may also interact with the orbital angular momentum of the electron to split the energies of the different levels, causing different transition energies to be … Read more
In a hydrogenic (one electron) species, the frequencies of the lines in the atomic absorption or emission spectra corresponds to transitions between different energy levels. In atoms with more than one electron, interaction between the electrons means that the transition energies are not simply related to differences between the energies of the different energy levels. The electrons in different … Read more
The total wavefunction of an atom is approximated as the sum of the wavefunctions of the individual atomic orbitals. This is only an approximation as it takes an average value of the electron-electron interactions between electrons in the different orbitals. The actual wavefunction describing the atom is the solution of Schrodinger’s equation: HΨn = EnΨn H is the Hamiltionian which describes … Read more
If we consider the first ionization energy of lithium, we find that its value, at 5.39 eV, would have to result from an effective nuclear charge of 0.63. This implies that there is a higher degree of screening than can be explained, as perfect screening would result in a Zeff value of one. In fact, the ground stateelectronic configuration of … Read more
This repulsion between electrons in many electron species which opposes the attraction of the electrons towards the nucleus, and which causes the energies of the atomic orbitals in many electron species to be lower in the hydrogenic species is known as electron shielding. In the hydrogenic species, the energy of an atomic orbital is given by: , where n is the principal quantum … Read more