Chemical Bonds The Formation of Compounds from Atoms

Chemical Bonds The Formation of Compounds from Atoms 

The atoms in vitamin C (ascorbic acid) bond together in a very specific orientation to form the shape of the molecule. The molecules collect together into a crystal, which has been photographed here in a polarized micrograph (magnified 200 times). 

11 The Valence Shell Electron Pair Repulsion (VSEPR) Model 

For centuries we ve been aware that certain metals cling to a magnet. We ve seen balloons sticking to walls. Why High-speed levitation trains are heralded to be the wave of the future. How do they function In each case, forces of attraction and repulsion are at work. 

Human interactions also suggest that opposites attract and likes repel. Attractions draw us into friendships and significant relationships, whereas repulsive forces may produce debate and antagonism. We form and break apart interpersonal bonds throughout our lives. 

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CHAPTER 11 CHEMICAL BONDS THE FORMATION OF COMPOUNDS FROM ATOMS... 

Chemical Bonds The Formation of Compounds from Atoms 213 Index 1-1... 

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 ... 

We shall see in Chapter 2 that the formation of a bond in an ionic compound depends on the removal of one or more electrons from one atom and their transfer to another atom. The energy needed to remove electrons from atoms is therefore of central importance for understanding their chemical properties. The ionization energy, /, is the energy needed to remove an electron from an atom in the gas phase ... 

Indications are increasing that the first chemical reaction step consists of the formation of a complex between the excited aromatic compound and the nucleophile (exciplex, excited it or a complex ). From this complex the reaction products are formed via one or more subsequent reaction steps. Such a pathway makes it possible to rationalize inter alia the large influence of the nucleophile on the position where it will eventually become attached through a-bonding at the ring carbon atom. 

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