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Polar covalent bond Chemical polarity, also known as bond polarity or simply polarity, is a concept in chemistry which describes how equally bonding electrons are shared between atoms. It is a physical property of compounds and affects other physical properties such as solubility, melting points and boiling points. Polarity also affects intermolecular forces, leading to some compounds or molecules within compounds being labelled as polar or non-polar. Polarity refers to the dipole-dipole intermolecular forces between the slightly positivelycharged end of one molecule to the negative end of another or the same molecule. Molecular polarity is dependent on the difference in electronegativity between atoms in a compound and the asymmetry of the compound's structure. For example, water is thought to be polar because of the uneven sharing of its electrons. However, methane is considered non-polar because the carbon shares the hydrogen molecules uniformally.

Ionic bond An ionic bond (or electrovalent bond) is a type of chemical bond based on electrostatic forces between two oppositely-charged ions. In ionic bond formation, a metal donates an electron, due to a low electronegativity, to form a positive ion or cation. In ordinary table salt (NaCl), the bonds between the sodium and chloride ions are ionic bonds. Often ionic bonds form between metals and non-metals. The non-metal atom has an electron configuration just short of a noble gas structure. They have high electronegativity, and so readily gain electrons to form negative ions or anions. The two or more ions are then attracted to each other by electrostatic forces.

Covalent bond Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds. In short, attraction-to-repulsion stability that forms between atoms when they share electrons is known as covalent bonding. Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-metal bonding, agostic interactions, and three-center two-electron bonds.[1][2] The term covalent bond dates from 1939.[3] The prefix co- means jointly, associated in action, partnered to a lesser degree, etc.; thus a "co-valent bond", essentially, means that the atoms share "valence", such as is discussed in valence bond theory. In the molecule H2, the hydrogen atoms share the two electrons via covalent bonding. Covalency is greatest

between atoms of similar electronegativities. Thus, covalent bonding does not necessarily require the two atoms be of the same elements, only that they be of comparable electronegativity. Because covalent bonding entails sharing of electrons, it is necessarily delocalized. Furthermore, in contrast to electrostatic interactions ("ionic bonds") the strength of covalent bond depends on the angular relation between atoms in polyatomic molecules.

Non-polar covalent bond NON-POLAR BONDING results when two identical non-metals equally share electrons between them. One well known exception to the identical atom rule is the combination of carbon and hydrogen in all organic compounds.

Chemical Bond Chemical bond, mechanism whereby atoms combine to form molecules. There is a chemical bond between two atoms or groups of atoms when the forces acting between them are strong enough to lead to the formation of an aggregate with sufficient stability to be regarded as an independent species. The number of bonds an atom forms corresponds to its valence. The amount of energy required to break a bond and produce neutral atoms is called the bond energy. All bonds arise from the attraction of unlike charges according to Coulomb's law; however, depending on the atoms involved, this force manifests itself in quite different ways. The principal types of chemical bond are the ionic, covalent, metallic, and hydrogen bonds. The ionic and

covalent bonds are idealized cases, however; most bonds are of an intermediate type.

Ionic Bond A chemical bond is a mutual attraction between the nuclei and valence electrons of two different atoms. This attraction results in the two atoms binding together. An ionic bond, also called an electron-transfer bond, is a type of chemical bond that is a result of the electromagnetic attraction between ions of opposite charges, i.e., a cation (a positively charged ion) and an anion (a negatively charged ion). An ion is an atom or group of atoms that has acquired an electrical charge due to the loss or gain of electrons. In an ionic bond, an atom gives or receives electrons from another atom. This is in contrast to covalent bonding, where two atoms share electron pairs between them. An ionic compound consists of anions and cations combined such that the total charge of the molecule is zero. All salts are ionic compounds. One characteristic that both ionic and covalent compounds share is that they adhere to the octet rule. The octet rule is the principle that describes the bonding in atoms. Individual atoms are unstable unless they have an octet of electrons in their highest energy level. The electrons in this level are called valence electrons. When atoms gain, lose, or share electrons with other atoms, they satisfy the octet rule and form chemical compounds. Ionic bonding occurs when one atom transfers electrons to another atom. In doing so, the atoms may achieve a complete outer energy level, satisfying the octet rule. During the formation of an ionic bond, one atom gains electrons and the other atom loses electrons. As a result, the atoms gain an electric charge. The atom that gains electrons gains a negative charge, becoming an anion. The atom that loses electrons gains a positive charge, becoming a cation. An example of this is the ionic bond that is formed between sodium (Na) and fluorine (F) to make sodium fluoride, NaF. A fluorine atom has seven valence electrons. It needs one more to have a complete outer energy level and satisfy the octet rule. If it gains this electron, it will become a negatively charged fluorine anion (F-). A sodium atom has only one valence electron. If it loses this electron, it is left with a complete outermost energy level that satisfies the octet rule. At the same time, it becomes a positively charged sodium cation (Na+). As the sodium

atom loses its electron, the fluorine atom picks it up. The two ions now have opposite charges and attract each other. This electromagnetic attraction is quite strong and holds the ions together, forming sodium fluoride. This binding of the two ions is called an ionic bond.

Covalent Bond A single covalent bond is created when two atoms share a pair of electrons. There is no net charge on either atom; the attractive force is produced by interaction of the electron pair with the nuclei of both atoms. If the atoms share more than two electrons, double and triple bonds are formed, because each shared pair produces its own bond. By sharing their electrons, both atoms are able to achieve a highly stable electron configuration corresponding to that of an inert gas. For example, in methane (CH4), carbon shares an electron pair with each hydrogen atom; the total number of electrons shared by carbon is eight, which corresponds to the number of electrons in the outer shell of neon; each hydrogen shares two electrons, which corresponds to the electron configuration of helium. Covalent bonds are of particular importance in organic chemistry because of the ability of the carbon atom to form four covalent bonds. These bonds are oriented in definite directions in space, giving rise to the complex geometry of organic molecules. If all four bonds are single, as in methane, the shape of the molecule is that of a tetrahedron. The importance of shared electron pairs was first realized by the American chemist G. N. Lewis (1916), who pointed out that very few stable molecules exist in which the total number of electrons is odd. His octet rule allows chemists to predict the most probable bond structure and charge distribution for molecules and ions. With the advent of quantum mechanics, it was realized that the electrons in a shared pair must have opposite spin, as required by the Pauli exclusion principle. The molecular orbital theory was developed to predict the exact distribution of the electron density in various molecular structures. The American chemist Linus Pauling introduced the concept of resonance to explain how stability is achieved when more than one reasonable molecular structure is possible: the actual molecule is a coherent mixture of the two structures

Polar Covalent Bonds

Covalent bonds involve the sharing of electrons between atoms. Consider the term "sharing". Does this mean equal sharing or unequal sharing? Think about sharing a Kit Kat chocolate bar with a friend. Does this mean that both of you get 2 fingers from this chocolate bar or could you have 3 fingers and give your friend only 1 finger? Would that be sharing? Sure! Sharing does not mean that the sharing was done equally! The sharing could be equal or it could be unequal and still be called sharing. If the electron pair that is shared between two atoms spends more time with one atom than the other, then we have a polar covalent bond. In a polar covalent bond, the atom that has the electron pair more of the time will be more negative than a neutral atom. It is said to be slightly negative and is given the label of (meaning slightly negative). The atom that gets the electron pair less of the time will be lacking a negative some of the time so it is given the label (meaning slightly positive). These labels are placed above the elements symbols when you draw a structural formula for a compound.

Non-Polar Covalent Bonds NON-POLAR BONDING results when two identical non-metals equally share electrons between them. One well known exception to the identical atom rule is the combination of carbon and hydrogen in all organic compounds. HYDROGEN:The simplest non-polar covalent molecule is hydrogen. Each hydrogen atom has one electron and needs two to complete its first energy level. Since both hydrogen atoms are identical, neither atom will be able to dominate in the control of the electrons. The electrons are therefore shared equally. The hydrogen covalent bond can be represented in a variety of ways as shown on the right: The "octet" for hydrogen is only 2 electrons since the nearest rare gas is He.

The diatomic molecule is formed because individual hydrogen atoms containing only a single electron are unstable. Since both atoms are identical a complete transfer of electrons as in ionic bonding is impossible. Instead the two hydrogen atoms SHARE both electrons equally.