Electronegative elements bonding

Fluorine and oxygen are the most electronegative elements. Bonds between these elements and all the metals have considerable ionic character, and in most cases are predominantly ionic. 

It should be noted that uncoordinated allylphosphine does not cyclise when treated with initiator, This gives evidence for the kinetic coordination template effect operating in this process. In conditions of kinetic control (enforced by spatial effects resulting from coordination to the metal), macrocyclic product formation by addition of P-H to the C=C double bond of a neighbouring coordinated allylphosphine proceeds contrary to Markovnikov s rule (phosphorus as a more electronegative element bonded to a less substituted carbon atom). This template process is notable for its exceptional regiospecific character in that the formation of Markovnikov addition products is not detected. 

When two atoms that differ m electronegativity are covalently bonded the electrons m the bond are drawn toward the more electronegative element... 

Hydrogen Bond Formation. This faciUtates adsorption if the mineral and the adsorbate have any of the highly electronegative elements S,0,N,F, and hydrogen. A weak (physical) bond is estabflshed between the sohd wall and the reagent through the alignment of the cited elements. 

One-bond couplings ( /ch) in saturated systems do not seem to have been investigated extensively. The value for cyclohexane (an average of couplings to axial and equatorial protons) iSk 123 Hz, and is increased by substitution adjacent to the carbon by an electronegative element, as with the aromatic systems discussed above. 

Electronegativity (Section 1.5) A measure of the ability of an atom to attract the electrons in a covalent bond toward itself. Fluorine is the most electronegative element. 

Two types of chemical bonds, ionic and covalent, are found in chemical compounds. An ionic bond results from the transfer of valence electrons from the atom of an electropositive element (M) to the atom(s) of an electronegative element (X). It is due to coulombic (electrostatic) attraction between the oppositely charged ions, M (cation) and X (anion). Such ionic bonds are typical of the stable salts formed by combination of the metallic elements (Na, K, Li, Mg, etc.) with the nonmetallic elements (F, Cl, Br, etc.). As an example, the formation of the magnesium chloride molecule from its elemental atoms is shown by the following sequence ... 

Inductive effect (Sections 2.1, 6.9. 16.4) The electron-attracting or electron-withdrawing effect transmitted through a bonds. Electronegative elements have an electron-withdrawing inductive effect. 

In principle, any molecule or anion with an unshared pair of electrons can act as a Lewis base. In other words, it can donate a lone pair to a metal cation to form a coordinate covalent bond. In practice, a ligand usually contains an atom of one of die more electronegative elements (C, N, O, S, F, Cl, Br, I). Several hundred different ligands are known. Those most commonly encountered in general chemistry are NH3 and HzO molecules and CN , Cl-, and OH- ions. 

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