Presentation on theme: "Chemical bond : the is the attractive force that holds two or an ext atoms with each other in a molecule or ion. Why do atom Combine? 1. Network attractive force between."— Presentation transcript:




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1 chemical bond : that is the attractive pressure that holds 2 or an ext atoms together in a molecule or ion. Why execute atom Combine? 1. Net attractive force in between atoms: 2. Lowering of energy of combine atoms: the process of chemical bonding between atoms decreases the power of the combining atoms and gives rise to the formation of a mechanism which has lower energy and hence has greater stability

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2 3. Octet dominance or rule of eight: Kössel and also Lewis in 1916 developed crucial theory of chemical combination between atoms well-known as digital theory of chemistry bonding. ‘According come this, atom can combine either by carry of valence electron from one atom to one more (gaining or losing) or by share of valence electrons in stimulate to have actually an octet in your valence shells. This is recognized as octet rule’.

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3 limitations of the Octet Rule:  The incomplete octet the the central atom: In some compounds, the number of electrons neighboring the main atom is much less than eight. This is specifically the situation with elements having less than four valence electrons. Examples are LiCl, BeH2 and also BCl3.  Li, Be and B have actually 1,2 and 3 valence electron only. Some various other such compounds space AlCl3 and also BF3.  Odd-electron molecules: In molecules v an odd number of electrons favor nitric oxide, NO and nitrogen dioxide, NO 2, the octet preeminence is not satisfied for every the atoms.

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4  The expanded octet: In a number of compounds of aspects in 3 rd period of routine table, there are an ext than eight valence electrons around the main atom. This is termed together the expanded octet. Obviously the octet rule does not use in together cases. Some of the examples of such compounds are: PF5, SF6, H2SO4 and a number of coordination compounds.

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5  species of chemistry Bond Initially, chemistry bonds can be divided into 2 types: strong bonds and also weak bonds.  strong Bonds: In this bonds, the bonding atom rearrange (transfer or share) their outermost covering electrons to attain the electron configuration of noble gases. These include following four types of bonds:  Ionic link  Covalent shortcut  name: coordinates (covalent) shortcut &  Metallic bond.  Weak Bonds: In these bonds, the bonding atoms execute not lose their identity. These include following two species of bonds:  Hydrogen link &  van der Waal’s forces.

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6 chemistry BOND (Continued) Ionic or Electrovalent bond  an interpretation  The ionic or electrovalent bond is the chemistry bond formed between two atom by the carry of one or much more valence electron from one atom come the other.  In various other words, Ionic or electrovalent shortcut is the electrostatic attraction between the cation (+ve ion) and also anion (  ve ion) produced by electron-transfer between two atoms.

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7 chemical BOND (Continued)  Some examples of Ionic Compounds: NaCl, MgO, CaF 3, MgCl 2, CaO 2, Al 2 O 3

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8 1)No. That valence electrons: A A + (1,2, or 3 valence electrons) IA, IIA and also IIIA B B - (5, 6 or 7 valence electrons) VA, VIA & VIIA 2) The ionisation energy of the steel atom must be low: The minimum lot of power required to remove the most loosely tied electron Ionisation energy A+ power required A + +e - ( ionisation energy ) short I. Power easy formation of ionic bond factors favoring the development of ionic compound

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9 3) digital affinity the the non-metal must be high: The lot of energy released when an electron is added to a neutral isolated gaseous atom electron affinity. B + e - B - + energy released (electron affinity) 4) The lattice energy of the ionic compound created should it is in high: the power released when one gram mole that a decision is formed from the gaseous ion is referred to as the lattice energy of the crystal. A + (1 mole) + B - (1 mole) A + B -

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10 higher the worth of lattice power of a crystal, the higher is the ease of its formation greater will certainly be the security of the ionic decision 5) Electronegativity distinction of A and also B must be high: A difference of 2 or more is essential for the development of an ionic bond in between atoms. Nature of ionic shortcut : 1)Crystalline state: ionic crystals space clusters of ion in the crystal lattice. Every Na + is surrounded by equally spaced six Cl - ions inserted at the corners the a continual octahedron and an in similar way each Cl - is surrounded by same spaced six Na + placed at the corners of one octahedron. 2)Electrical conductivity : Ionic link in soild state carry out not conduct electrical power Ionic compound in solution/ unify state conduct electrical power 

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11 3) Isomorphism: Ionic solids consisted of of ions through identical digital configuration present an identification of crystalline form which is called isomorphism e. G. (a) salt fluoride & magnesium oxide + Na + (2, 8) F - (2,8) Mg +2 (2,8) O 2- (2,8) (b) Calcium chloride & Potassium sulphide Cl - (2,8,8) Ca +2 (2,8,8) Cl - (2,8,8) K + (2,8,8) S 2- (2,8,8) K + (2,8,8) 4) Dielectric constant: The substances containing ionic bonds have actually high dielectric constant. 5) High melting and also boiling points: really high lot of power (in the type of heat) is required. E.g. NaCl boils at 1470 0 C CCl4 boils at 77 0 C 6) Solubility in polar and non-polar solvents: ionic compound are generally an ext soluble in polar (H 2 O, NH 3 ) 보다 in non polar solvents(C 6 H 6, CCl 4 ). The electrostatic force of attraction in ionic heavy is reduced by the high value of dielectric constant

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12 the the polar solvent ions have the right to move freely and interact through solvent molecules to form the solvated ions. Restrictions of ionic shortcut Electrovalency: Electrovalency of an aspect is same to the number of electrons lost by one atom that that aspect in creating a (+) ion or obtained by that in developing a negative ion, both having actually the noble gas configuration (S 2 ns 6 ). Varible electrovalency 1) turbulent configuration loss of electron from Fe, Co, Ni, Cu remaining part is called the core (unstable) additional loss the electron indigenous the core variable electrovalency

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13 e.g. Fe (26) 2,8,14,2 or 2,8, 3S 2 3P 6 3d 6 4S 2 Fe +2 (24) 2,8,14 or 2,8, 3S2 3P6 3d6 Fe +3 (23) 2,8,13 or 2,8, 3S2 3P6 3d5 2) many cations carry out not constantly have inert gas structure. There space cations which have actually outer S 2 ns 6 d 10 CU+ Zn+2 3S 2 3P 6 3d 10 Ag+ cd+2 4S 2 4P 6 4d 10 Cu 1S 2 2S 2 2P 6 3S 2 3P 6 3d 10 4S 1 Cu+ 1S 2 2S 2 2P 6 3S 2 3P 6 3d 10 Cu++ 1S 2 2S 2 2P 6 3S 2 3P 6 3d 9

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14 3) Inert Electron Pair Effect: Is just the reluctance that ns orbit electron pair to take component in bonding. E.g. In situation of p-block elements the valency that +3 becomes an ext predominant 보다 +5 together the ns electrons perform not get involved in bonding. Example: back the usual oxidation sate for aspects in group four is +4, most elements in the group can also exist in oxidation state +2.This is since of the inert pair effect. In big atoms, such as those the tin and also lead some external shell electrons room not also shielded as those in the within core. Castle are because of this sucked into the inner main point of electrons and thus come to be inert. Group III A (G=3) Ga (+1, +3), In (+1, +3) TI (+1, +3) group IV A (G=4) Ge (+2, +4), Sn (+2, +4) Pb (+2, +4) group V A (G=5) together (+3, +5), Sb (+3, +5) Bi (+3, +5)

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15 The greater oxidation state for most of the elements is same to their team number, G when the reduced one is same to (G- 2). G as soon as all the ns and also np electrons from ns 2 ns x construction of ns block elements(x= 1, 2,3 and also 4 for the facets of gr. IIIA, IVA, VA and VA, respectively) are lost. (G-2) when only the np electrons room lost and the ns electron pair, due to its extra stability, stays inert, i.e. No lost. Together a pair of ns electron is referred to as inert electron pair and also the result caused by the is known as ‘Inert electron pair effect”.

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16 Dielectric constant: as soon as a dipolar or polar molecule is placed in one electrostatic field the positive end of the dipole is directed in the direction of the an unfavorable pole that the electric field and also vice versa. The oriented dipole oppose the field and the intensity of the electrical field is reduced. The reduced tendency is measure by the dielectric constant or the details inductive capacity of the polar substance. The substances containing ionic bonds have high dielectric constant.

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17  general Properties the Ionic compound  Ionic link exist together crystals.  They space solid in room temperature.  The crystals room hard and also brittle.  They have actually high melt points.  They room soluble in water.  In molten state and also aqueous solution, they are an excellent conductor that electricity.  The ionic compounds do not show isomerism.  The reactions in between the ionic link take place with good speed.

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18 chemistry BOND (Continued) Covalent shortcut  meaning  Covalent shortcut (also referred to as electron-pair bond) might be identified as the chemistry bond or attractive force between atoms that results from share of one electron-pair. Every of the 2 bonding atom contributes one electron to the electron-pair (and has equal insurance claim on the shared electron-pair). The shared electron pair is shown by a dash (  ) between the two bonded atoms.  to state in a various way, a covalent bond in between two atoms outcomes from the overlap the an orbit of one atom through an orbital of one more atom. As the 2 orbitals overlap, lock share the same region in room and a new orbital (molecular orbital) is formed.  two atoms might bind with each other by one, two or also three covalent bonds.  The link containing a covalent shortcut are recognized as covalent compounds.

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19  conditions for development of Covalent Bond: The problems favorable for the formation of covalent binding are:  number of valence electrons: every of the atoms A and B should have 5, 6 or 7 electrons (1 for H) so the both can accomplish stable octet by sharing 3, 2 or 1 electron-pair respectively. The non-metals the the teams VA, VIA and VIIA respectively meet this condition.  same electronegativity: The two atoms need to have almost equal electro negativity (in other words, same attraction for electrons).  High Ionization energy: The atoms v high ionization energy are i can not qualify of loosing electron to kind cations but they can kind covalent bonds between them  High nuclear fee and little intermolecular street

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20 chemical BOND (Continued)  basic Properties of Covalent compound  physics state: normally gases, liquids or relatively soft solids in ~ room temperature.  decision Structure: a.Giant molecules – whereby every atom is external inspection with other atoms by covalent bonds. E.g: diamond b.Separate great – the covalent link containing different layers are stated to have layer lattice structure.e’g: graphite  Melting suggest & boiling Point: Low melting points or boil points.  Neither hard nor brittle: Covalent compounds room soft and waxy as they contain separate crystal lattice. No repulsion pressures are present between the layers therefore the covalent crystals space easily damaged

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21  Solubility : usually soluble in nonpolar necessary solvents (e.g. Benzene, ether) and also insoluble in water.  Conductivity: Non-conductor the electricity.  Isomerisom: exhibit isomerism.  molecule reactions: since there room no solid electrical pressures acting in covalent compound to speed up the reaction in between molecules, the molecule reactions space slow.  basic Properties the Covalent compounds

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22 chemistry BOND (Continued)  varieties of Covalent Bonds: In terms of the molecule orbitals formed, there are two main species of covalent bonds: Sigma (  ) bonds and also pi (  ) bonds. Sigma bond  A sigma bond is formed by linear (end-to-end) overlap the orbitals.  All single covalent bonds and one bond in lot of covalent bonds room sigma bonds.  It might be derived by:  the overlap of two s orbitals  the overlap of a ns orbital and an s orbital, or  the overlap of 2 p obitals. Pi binding  A pi link is formed by parallel or (side-by-side) overlap of p orbitals.  A pi bond has two lobes favor p orbitals  one fifty percent of the link lies above the airplane containing the two nuclei and also the other fifty percent lies below the plane.  One link in twin bonds and also two bonds in triple bonds space pi bonds.

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23 chemistry BOND (Continued) Sigma bondPi shortcut 1It is developed by end-to-end overlapping the half-filled atomic orbitals. It is formed by the sidewise overlapping that half-filled p obitals. 2Overlapping takes ar along the inter-nuclear axis. Overlapping takes location perpendicular come the inter-nuclear axis. 3The extent of overlapping is big and the bond formed is stronger. The level of overlapping is smaller and also the bond developed is weaker. 4There is complimentary rotation roughly the sigma bond and also so no geometrical isomerism is possible. Over there is no free rotation around the pi bond and so geometrical isomerism possible. 5Both s and also p orbitals deserve to participate in sigma shortcut formation. Just p orbitals get involved in the formation of pi bonds.  Differences between the Sigma and also Pi bonds

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24 chemical BOND (Continued)  Differences/ Distinctions in between Ionic Bonds and Covalent binding CharacteristicsIonic BondCovalent link 1. Formation of Bond formed by move of electrons from a metal to a nonmetal atom. Formed by share of electrons between non-metal atoms. 2. Physics StateIonic compounds space solids in ~ room temperature. Covalent compounds room gases, liquids or soft solids. 3. Hardness & Brittleness Ionic compounds are hard and brittle.Covalent compounds are soft and are much readily broken. 4. SolubilityIonic compounds are soluble in water however insoluble in organic solvents. Covalent compounds are insoluble in water however soluble in necessary solvents. 5. Melting & Boiling points Ionic compounds have high melting and also boiling points. Covalent compounds have actually low melting and boiling points. 6. Conduction of electricity Ionic compound conduct power in molten state or aqueous solution. Covalent compounds do not command electricity. 7. IsomerismIonic compounds execute not show isomerism. Covalent link can display isomerism. 8. ReactivityReactions the ionic compounds are fast. Reaction of covalent compounds room slow.

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25 Nonpolar & Polar Covalent bonds  Nonpolar Covalent Bond:  This is a covalent bond in which the electron pair is mutual equally by the linked atoms.  it happens as soon as the 2 atoms are similar and so have the very same electronegativity or zero electronegativity difference.  This is also called homopolar covalent shortcut or merely covalent bond. Together a issue of fact, the is the pure or true covalent bond.

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26  Polar covalent bond:  This is a covalent shortcut in which the electron pair is mutual unequally through the connected atoms so the they gain a partial hopeful and negative charge.  This happens as soon as the covalent bond links two dissimilar atom which have various electronegativity values and also so uneven attraction because that the electron pair.  The molecules which have polar covalent bonds are known as polar molecules. Instances of polar molecules include HCl, H 2 O, NH 3 etc.  A polar molecule, v its optimistic and an adverse charge centers or electric poles at the end of the covalent bond, becomes dipolar and also hence is called a dipole (two poles). The dipole the a bond may be presented by an arrow from optimistic to an adverse with a crossed tail.

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27 name: coordinates Bond  meaning  coordinate bond is a covalent bond, i beg your pardon is formed by the common sharing of two electrons both of i beg your pardon are noted by one of the linked atoms (or ions). Name: coordinates bond is likewise sometimes referred to as name: coordinates covalent link or dative bond.  If one atom has actually an unshared pair of electrons (lone pair) and also another atom is quick of 2 electrons than the secure number, a coordinate bond is formed. The atom which donates the lone pair is referred to as the donor and also the atom i beg your pardon accepts that the acceptor. The coordinate bond is represented by an arrow which points away from the donor to the acceptor.  The link containing a coordinate bond are dubbed coordinate compounds and the molecule or ion that contains the donor atom is referred to as the ligand.

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28  Illustration of formation of a name: coordinates bond: The formation of covalent bond in between two atoms, speak A and B, have the right to be shown as follows: 1) The atom acting as a donor should have a lone pair that electrons. 2) The atom acting together an agree should have actually a vacant orbital to expropriate the electron pair donated by the donor.  conditions for the development of a name: coordinates bond conditions necessary because that the formation of a name: coordinates bond are:

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29 features of coordinate covalent compound: (1)Their melting and boiling point out are higher than completely covalent compounds and also lower 보다 purely ionic compounds. (2) These are sparingly soluble in polar solvent choose water yet readily soluble in non-polar solvents. (3) choose covalent compounds, this are likewise bad conductors that electricity. Their solutions or fused masses perform not permit the i to electricity. (4) The bond is rigid and directional.

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30  Some instances of name: coordinates compounds or ions NH 4 +, H 3 O +, BF 4 , enhancement compound of NH 3 through BCl 3, CH 3 NO 2, therefore 2 & so 3, Al 2 Cl 6, therefore 4 2 , O 3, CO.  representation of coordinate Bond formation by Lewis Symbol and also Structure

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31 Metallic link Metallic link is the attractive force, acting in between the positive steel ions and also surrounding easily mobile electrons, the holds the metal atoms together in a metal crystal.

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32 Hydrogen shortcut  Definition: Hydrogen bond refers to the electrostatic attraction between (i) a H atom covalently bonded to a extremely electronegative atom X (O, N or F) and (ii) a lone pair of electron on X in an additional molecule  species of Hydrogen Bond: Hydrogen bond is of 2 types: i) Intermolecular hydrogen bond (association) & ii) Intramolecular hydrogen bond

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33  Intermolecular Hydrogen Bond: as soon as hydrogen bonding occurs in between two molecule of the very same or various compounds, that is referred to as intermolecular hydrogen bonding. E.g. Hydrogen bonding in between the molecule of H 2 O, NH 3 or HF.  Intermolecular Hydrogen Bond: If hydrogen bonding takes place in between an H-atom and an electronegative atom in ~ the same molecule (e.g. In o-nitrophenol), that is referred to as intramolecular hydrogen bonding.

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34  Definition: valve der Waals pressures are an extremely short-lived inter-molecular attractive pressures which are believed to exist in in between all kinds of atoms, molecules and also ions when they are sufficiently near to each other.  Types: There are four varieties of valve der Waals forces. These are:  Dipole-dipole interaction (Keesom forces): these are found in polar molecules (e.g. HCl) and are the the strongest of all van der Waals forces.  Ion-dipole interactions: e.g. Between Na + / Cl  and H 2 O as soon as NaCl dissolves in H 2 O.  Dipole-induced dipole interactions (Debye forces): this are discovered in a mixture include polar and also non-polar molecules.  Instantaneous dipole-induced interaction (London forces): this are discovered in nonpolar molecules, e.g. Diatomic gases choose H 2, O 2, Cl 2, N 2 etc. And monoatomic noble gases prefer He, Ne, Ar etc. Valve der Waals pressures

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35 chemical BOND (Continued)

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37 HYBRIDIZATION  Definition:  Hybridization might be defined as the phenomenon of mix up (or merging) of pure orbitals of practically equal power on an atom, giving rise come equal variety of entirely new orbitals, which space equal in energy and identical in shape.  It may be listed here the it is the orbitals the undergo hybridization and not the electrons. For example, 4 orbitals of an oxygen atom (1s 2, 2s 2, 2p x 2, 2p y 1, 2p z 1 ) belong to second level (i.e. 2s, 2p x, 2p y, 2p z ) deserve to hybridize to give four hybrid orbitals  2 of which have actually two electron (as before) and also the various other two have one electron every (as before).  importance of the principle of hybridization: The principle of hybridization is essential for explaining the propensity of atoms like Be, B and C to form bonds and also the form or geometry of their molecules.  species of Hybridization: depending upon the number and also nature that the orbitals undergoing hybridization, we have various species of hybrid orbitals. For instance, s, p and also d orbitals of simple atoms may hybridize in the following manner: (a) sp hybridization, (b) sp 2 hybridization, (c) sp 3 hybridization and (d) Hybridization including d orbitals, e.g. Dsp 3, d 2 sp 3, dsp 2

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38 HYBRIDIZATION (Continued) It entails mixing of one s and a ns orbital giving rise to 2 hybrid orbitals recognized as sp hybrid orbitals.  The resulting orbitals species themselves along a line at an angle of 180  (between the axes the the 2 orbitals) and are, therefore, regularly referred to as direct hybrid orbitals. Sp hybridization

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39 HYBRIDIZATION (Continued)  examples of compounds experience sp hybridization: BeF 2, ethynes (e.g. CH  CH)

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40 HYBRIDIZATION (Continued) sp 2 hybridization  It entails mixing of one s and also two p orbitals offering rise to three new orbitals dubbed sp 2 hybrid orbitals.  The sp 2 hybrid orbitals resemble in form with the of sp hybrid orbitals but are contempt fatter.  The three orbitals space arranged in the same aircraft at an edge of 120º come one another and also hence sp 2 hybrid orbitals are likewise called trigonal hybrid orbitals and the process trigonal hybridization.

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41 HYBRIDIZATION (Continued)  example of molecule undergoing sp 2 hybridization: BF 3, ethenes (e.g. CH 2  CH 2 )

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42 HYBRIDIZATION (Continued)

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43  It involves mixing of one s and also three p orbitals of one atom, offering rise to four brand-new orbitals called sp 3 hybrid orbitals.  They room of the same shape the the previous 2 types, yet bigger in size.  The 4 orbitlas room arranged in the room in the type of a continuous tetrahedron at edge of 109.5° between them, and because of your tetrahedral disposition, this type of hybridization is also called tetrahedral hybridization. Sp 3 hybridization

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44 HYBRIDIZATION (Continued)  instances of molecule undergoing sp 3 hybridization: CH 4, NH 3, H 2 O

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45 HYBRIDIZATION (Continued)

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46 Bond edge : it is characterized as the angle in between the orbitals comprise bonding electron pairs about the main atom in a molecule/complex ion.

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Bond edge is to express in degree which can be experimentally established by spectroscopic methods.

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