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The Sri Lankan Advanced Level (A-level), formerly known as the Higher School Certificate (HSC), is a General Certificate of Education (GCE) qualification exam in Sri Lanka, similar to the British Advanced Level. It is conducted annually by the Department of Examinations under the Ministry of Education.
On the molecular level, the interlocked molecules cannot be separated without the breaking of the covalent bonds that comprise the conjoined molecules; this is referred to as a mechanical bond. Examples of mechanically interlocked molecular architectures include catenanes , rotaxanes , molecular knots , and molecular Borromean rings .
A bond of higher bond order also exerts greater repulsion since the pi bond electrons contribute. [10] For example in isobutylene, (H 3 C) 2 C=CH 2, the H 3 C−C=C angle (124°) is larger than the H 3 C−C−CH 3 angle (111.5°). However, in the carbonate ion, CO 2− 3, all three C−O bonds are equivalent with angles of 120° due to resonance.
The strong bonding of metals in liquid form demonstrates that the energy of a metallic bond is not highly dependent on the direction of the bond; this lack of bond directionality is a direct consequence of electron delocalization, and is best understood in contrast to the directional bonding of covalent bonds.
The A-level (Advanced Level) is a subject-based qualification conferred as part of the General Certificate of Education, as well as a school leaving qualification offered by the educational bodies in the United Kingdom and the educational authorities of British Crown dependencies to students completing secondary or pre-university education. [1]
A solid with extensive hydrogen bonding will be considered a molecular solid, yet strong hydrogen bonds can have a significant degree of covalent character. As noted above, covalent and ionic bonds form a continuum between shared and transferred electrons; covalent and weak bonds form a continuum between shared and unshared electrons.
The MO diagram for dihydrogen. In the classic example of the H 2 MO, the two separate H atoms have identical atomic orbitals. When creating the molecule dihydrogen, the individual valence orbitals, 1s, either: merge in phase to get bonding orbitals, where the electron density is in between the nuclei of the atoms; or, merge out of phase to get antibonding orbitals, where the electron density ...
A chemical bonding model is a theoretical model used to explain atomic bonding structure, molecular geometry, properties, and reactivity of physical matter. This can refer to: VSEPR theory, a model of molecular geometry. Valence bond theory, which describes molecular electronic structure with localized bonds and lone pairs.