Chemical bonding

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WELCOME

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b

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Represents

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No one wants to be alone08-Dec-13

Chemical bonding

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Chemical bonding.Types of bonds.Octect rule.Valence bond theory.VSEPR theory

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Bond

Forms of Chemical Bonds

Ionic bond Covalent bond

Ionic—complete transfer of electrons from one atom to anotherCovalent—electrons shared between atoms

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Na- -

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Bond- forces that hold groups of atom

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The Octet Rule – Ionic Compounds

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Ionic compounds form so that each atom, by gaining or losing electrons, has an octet of electrons in its highest occupied energy level.

Metals lose electrons to form positively-charged cations

Nonmetals gains electrons to form negatively-charged anions

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Ionic Bonding:The Formation of Sodium Chloride

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Sodium has 1 valence electron

Cl: 1s22s22p63s23p5 Na: 1s22s22p63s1

Chlorine has 7 valence electrons An electron transferred gives each an octet

Cl17

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Na- -

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Na+ 1s22s22p6This transfer forms ions, each with an octet forms

Cl- 1s22s22p63s23p6

The resulting ions come together due to electrostatic attraction forming Nacl

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Properties of Ionic Compounds

Structure: Crystalline solids

Melting point:

Generally high

Boiling Point:

Generally high

Electrical Conductivity:

Excellent conductors, molten and aqueous

Solubility in water:

Generally soluble08-Dec-13

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Covalent Bonding

The bond arises from the mutual attraction of 2 nuclei for the same electrons.

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HB+ HAHBHA

A covalent bond is a balance of attractive and repulsive forces.

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Covalent Bond Formation- valence bond theory and it’s postulates

A covalent bond is formed by the overlap of orbital's of one atom ,with the orbital of another atom

1. Only an orbital with unpaired electrons is eligible for overlapping2. For orbital to overlap, the electrons in overlapping orbital's should spin in the opposite direction3. After overlapping the shape of orbital's change such that a greater electron density Appear between the nuclei of atoms along internuclear axis

Conditions for overlapping are :

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The factor which decides the strength of covalent bond is the extent of overlap, it depends on the shape of orbital's .The spherical ‘s’orbital’s can not overlap efficiently, where as the extent of overlapping the dumb bell shaped p orbital's more

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Strength of covalent bond

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Overlapping Of Orbital'ss-s overlap It involves mutual overlap of half filled s-orbitals of the atoms approaching to form a bond. s-p overlap It involves mutual overlap of half filled s-orbitals of the one atom with half filled p-orbital of the other..p-p overlap It involves mutual overlap of half filled p-orbitals of the two atoms.

Order of strength of overlapping : p-p > s-p > s-s 08-Dec-13

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Sigma bond (σ) Sigma bond is formed by an axial or head-on overlapping of pure atomic orbital's It is end to end overlap. Sigma bonds are re presented by Greek latter σ Examples: (σ bond)

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Pi bond (∏) A pi body is formed by the sidewise overlapping of pure atomic orbital's.the extent of overlapping is less, hence a pi bond is weaker than σ bond

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Bond and Lone Pairs

A bond pair means 2 electrons involved in bondingAlone pair means a pair of 2 electrons not involved in

bonding

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••H Cl

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This is a LEWIS ELECTRON DOT structure.

shared or bond pair

Unshared orlone pair (LP)

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VSEPR theory and Molecular Geometry

This theory helps in explaining the shapes of single covalent molecules. according to this theory the Various electron pairs around a central atom orient themselves in a such way that there is minimum repulsion and maximumstabilityThe decreasing order of repulsions among electron pairs is as under

Lone pair -Lone pair > Lone pair-Bond pair > Bond pair -Bond pair

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(Valence Shell Electron Pair Repulsion)

Predicting a VSEPR Structure1. Draw Lewis structure.

2. Put pairs as far apart as possible.

3. Determine positions of atoms from the way electron pairs are shared

4. Determine the name of molecular structure from positions of the atoms.

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Steric Number 1

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StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs 4 lone pairs

1linear

1 atom bonded to another atom

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Steric Number 2

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StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

2linear linear

2 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

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Steric Number 3

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StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

3trigonal planar bent / angular linear

3 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

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Steric Number 4

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StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

4tetrahedral

trigonal pyramid bent / angular linear

4 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

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Steric Number 5

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StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

5trigonal

bipyramidsawhorse /

seesaw t-shape linear

5 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

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Steric Number 6

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StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

6Octahedral square pyramid square planar

6 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

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Steric Number 7

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StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

7pentagonal bipyramidal

pentagonal pyramidal

7 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

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Thanks to all of you

08-Dec-13

2608-Dec-13

Best of luck to achieve the seat of IIT,

Good Night

Created by

Abhishek S. Vispute