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Structure of iodine heptafluoride, an example of a molecule with the pentagonal-bipyramidal coordination geometry. In chemistry, a pentagonal bipyramid is a molecular geometry with one atom at the centre with seven ligands at the corners of a pentagonal bipyramid. A perfect pentagonal bipyramid belongs to the molecular point group D 5h.
Residual topology [5] is a descriptive stereochemical term to classify a number of intertwined and interlocked molecules, which cannot be disentangled in an experiment without breaking of covalent bonds, while the strict rules of mathematical topology allow such a disentanglement.
Protein tertiary structure is the three-dimensional shape of a protein. The tertiary structure will have a single polypeptide chain "backbone" with one or more protein secondary structures, the protein domains. Amino acid side chains and the backbone may interact and bond in a number of ways. The interactions and bonds of side chains within a ...
The chemical bonding within the molecule is also shown, either explicitly or implicitly. Unlike other chemical formula types, [ a ] which have a limited number of symbols and are capable of only limited descriptive power, structural formulas provide a more complete geometric representation of the molecular structure.
A hairpin is a special case of a turn, in which the direction of the protein backbone reverses and the flanking secondary structure elements interact. For example, a beta hairpin connects two hydrogen-bonded , antiparallel β-strands (a rather confusing name, since a β-hairpin may contain many types of turns – α, β, γ, etc.).
The cornerstone of classical bonding theories is the Lewis structure, published by G. N. Lewis in 1916 and continuing to be widely taught and disseminated to this day. [3] In this theory, the electrons in bonds are believed to pair up, forming electron pairs which result in the binding of nuclei .
Theories of chemical structure were first developed by August Kekulé, Archibald Scott Couper, and Aleksandr Butlerov, among others, from about 1858. [4] These theories were first to state that chemical compounds are not a random cluster of atoms and functional groups, but rather had a definite order defined by the valency of the atoms composing the molecule, giving the molecules a three ...
Crystal structure of sodium chloride (NaCl) with sodium cations (Na +) in purple and chloride anions (Cl −) in green. The yellow stipples represent the electrostatic force between the ions of opposite charge. Ionic bonding is a type of electrostatic interaction between atoms that have a large electronegativity difference.