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Covalent Bonds

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Introduction

Covalent Bonds Covalent bonds are formed when atoms share electrons, one from each atom in a single bond, to form electron pairs, usually making their outermost shells up to eight electrons by this means. This would make them more stable, less reactive and an electronic structure like a noble gas. They are most frequently formed between pairs of non-metallic elements. Non-metallic elements usually have from four to eight electrons in their outermost shells, the so-called valency electrons, which are used for chemical bonding. In any given "full" shell of eight electrons, the electrons occur in four pairs, but in incomplete shells, the electrons exist singly where possible. Sometimes, atoms of elements form covalent bonds with other atoms of the same element. Thus two chlorine atoms form the chlorine molecule, Cl2, by sharing their unpaired electrons. In the case of oxygen (O2), there are two unpaired valency electrons in each atom, so that two electron-pair bonds are formed between the two atoms to complete their octet of electrons, a double bond. ...read more.

Middle

Ionic Bonds Ionic bonds are formed through the electrostatic attraction between two oppositely charged ions. This type of bond normally occurs between metallic and non-metallic elements. Metals typically have few valency electrons, and occur in groups I, II, and III of the periodic table; reactive non-metals typically have more electrons in their outermost shells, and occur in groups IV, V, VI, and VII. An ionic bond occurs when a metal loses all its valency electrons, leaving a positively charged ion with a noble gas structure, and a non-metal gains the number of electrons it requires to give it a noble gas structure, and becomes a negative ion. The ionic bond occurs by means of the attraction between these charged particles, but because there are, of course, millions and millions of them in any given sample, they do not just pair off to make simple "molecules". ...read more.

Conclusion

Every ion is strongly bonded to its neighbours, and the whole is thus held in a rigid lattice with a specific shape. They have high melting and boiling points. This is because the very strong bonding associated with ionic compounds means that much energy is required to break these bonds. They are soluble in water. This is because water is a so-called ionizing solvent, because of its polar nature. The water molecule is capable of attaching itself to both positive and negative ions, water is therefore capable of carrying away the ions into solution (in the form of "hydrated" ions), so that the solid eventually dissolves. Non-polar solvents do not dissolve ionic solids. Compounds containing ionic bonds also conduct electricity when in solution (water) or when molten. This is because both the solution and the molten compound contain ions that can move about when an electric current is passed through. Solid ionic compound cannot conduct electricity as the ions are held in their rigid lattice, and are not free to move. Shayon King ...read more.

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