CHEMICAL BONDING BY: SEENAM IFTIKHAR

Chemical bond is an effect that causes certain atoms to join together to form enduring structures that have unique physical and chemical properties.

DEFINITION:

EXAMPLE:

The importance of chemical bonding is nicely illustrated by the structures of the two compounds; ethanol and dimethyl-ether, both of which have the simplest formula C2H6O. The structural formulas reveal the very different connectivity's of these two molecules whose physical and chemistry properties are quite different:

IMPORTANCE:

Ionic bonding

PRESENTED BY: MAZNA SALEEM

Ionic Bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions. These ions represent atoms that have lost one or more electrons (known as cations) and atoms that have gained one or more electrons (known as anions).

IONIC BONDING

EXAMPLE

• Sodium (2,8,1) has 1 electron more than a stable noble gas structure (2,8). If it gave away that electron it would become more stable.

• Chlorine (2,8,7) has 1 electron short of a stable noble gas structure (2,8,8). If it could gain an electron from somewhere it too would become more stable.

Bonding in NaCl

HOW IT TRANSFERS???

EXAMPLE OF NaF...

EXAMPLE OF MgO...

BY: HIBA MUSHTAQ

INTRODUCTION

• Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell.

• Bond pair.• Lone pair.

OCTET RULE• The Octet Rule requires all atoms in a

molecule to have 8 valence electrons.

SINGLE BONDS• A single bond is when two electrons--one pair

of electrons--are shared between two atoms. It is depicted by a single line between the two atoms.

EXAMPLE 1: HCl

DOUBLE BONDS• A Double bond is when two atoms share two

pairs of electrons with each other. It is depicted by two horizontal lines between two atoms in a molecule.

EXAMPLE 2: Co2

TRIPLE BOND• A Triple bond is when three pairs of electrons

are shared between two atoms in a molecule. It is the least stable out of the three general types of covalent bonds.

EXAMPLE 3: ACETYLENE

POLAR COVALENT BOND• A Polar Covalent Bond is created when the

shared electrons between atoms are not equally shared. This occurs when one atom has a higher electronegativity than the atom it is sharing with.

• Examples: Water, Sulfide, Ozone, etc.

EXAMPLES

NONPOLAR COVALENT BOND• A Nonpolar Covalent Bond is created when

atoms share their electrons equally. This usually occurs when two atoms have similar or the same electron affinity.

• Examples of gas molecules that have a nonpolar covalent bond: Hydrogen gas atom, Nitrogen gas atoms, etc.

EXAMPLES

Co-Ordinate Covalent Bonding

Presented by Farah Deeba.BY: FARAH DEEBA

CO-ORDINATE COVALENT BOND

”A covalent bond in which both electrons come

from the same atom. Also known as dativecovalent bonding.”

The atoms which donates the electron to formit is called as the donor atom, while the atomwhich accepts the pair of electron for bonding iscalled as the acceptor atoms.

EXPLAINATION

EXAMPLES OF CO-ORDINATE BOND

• Lewis acid base reaction is an excellent example of the co-ordinate covalent bond. For example the bond- H3N: → BF3

-is a coordinate bond. Here nitrogen acts a donor atom.

The lone pair of electron in the nitrogen is donated tothe vacant p orbital of the boron. Here ammonia isLewis base and BF3 is Lewis acid.

EXAMPLES OF CO-ORDINATE BOND

Boron hydride-ammonia complex.

Here, the nitrogen atom becomes the donor. The hydrogen atom becomes the acceptor. The linkage between N and H atoms is called coordinate bond. It is represented by an arrow →.

AMMONIUM ION CO-ORDINATE BOND:

PROPERTIES

• Has all the characteristic of the covalent bond. • Have low boiling and melting point. • There are no columbic forces of attraction.• Does not conduct electricity in the liquid or in

the dissolved state. • Compounds are that much soluble in water. • As strong as other covalent bonds.

Metallic bond

BY: UFAQ HAMID

METALLIC BONDINGMetallic bonding is the electrostatic attraction between the positively charged atomic nuclei of metal atoms and the delocalized electrons in the metal.

PROPERTIES OF METALS1.Metals are shiny.2.Metals conduct electricity because electrons are free to move.3.Metals conduct heat because the positive nuclei are packed closely together and can easily transfer the heat.4.Metals have a high melting point because the bonds are strong and a high density because of the tight packing of the nuclei.

The outermost electrons for most metals are only loosely bound to their nuclei because of their relative remoteness from their positively charged cores. All valence electrons of a given metal combine to form a "sea" of electrons that move freely between the atom cores. The positively charged cores are held together by these negatively charged electrons. In other words, the free electrons act as the bond between the positively charged ions. Metallic bonds are non directional. As a consequence, the bonds do not break when a metal is deformed. This is one of the reasons for the high ductility of metals.The schematic representation of metallic bonding is show below. The valence electrons become dissociated with their atomic core and form an electron "sea" that acts as the binding medium between the positively charged ions.

Examples for materials having metallic bonds are most metals such as Cu, Al, Au, Ag etc. Transition metals (Fe, Ni etc.) form mixed bonds that are comprised of covalent bonds (involving their 3d-electrons) and metallic bonds. This is one of the reasons why they are less ductile than Cu, Ag and Au.

METALLIC BOND EXAMPLES

Ionic Bond Covalent Bond Metallic Bond

The transfer of electrons between two atoms having different electro negativities forms this bond.

This bond is formed by the mutual sharing of electrons between same or different elements .

This bond is formed due to the attraction between kernels and the mobile electrons in a metal lattice.

This is a strong bond due to electrostatic force of attraction.

This is also a fairly strong bond because the electron pair is strongly attracted by two nuclei.

This is a weak bond due to the simultaneous attraction of the electrons by a large number of kernels

This is a non-directional bond. This is a directional bond. This is a non-directional

bond.

This bond makes substances hard and brittle.

This bond makes substances hard and incompressible.

This bond make substances malleable and ductile.

COMPARISON OF IONIC BOND COVALENT BOND AND METALLIC BOND

BY: SHABANA RAEES

INTRA MOLECULAR FORCESThe intramolecular force is the sum of all the

forces holding a molecule or compound together.

These forces are stronger than intermolecular forces. Intramolecular forces are categorized into three types.1. Metallic bonding2. Ionic bonding3. Covalent bonding

METALLIC BONDING:This type of bonding is formed when metal atoms share delocalized electrons.IONIC BONDING:This type of bonding is formed when metal atom donate one or more electrons to non metal atoms. An electrostatic attraction builds between the two ions, which is known as ionic bonding.

COVALENT BONDING: Covalent bonding involves sharing a pair of electrons. By sharing a pair of electrons both atoms gain a stable electron configuration state.

WHY IS INTRAMOLECULAR FORCES GREATER THAN INTERMOLECULAR

FORCES?Intramolecular forces generally involve covalent bonds, wherein electrons are shared, and atoms are relatively close to each other. Proximity of the atoms and the electron sharing make the forces strong. Intermolecular forces generally involve weak electrostatic interaction, and atoms are farther from each other, rendering the forces weaker than the intramolecular variety. In general, the force between two objects is proportional to the inverse of the square of the distance between them, or Force ~= 1/(distance*distance). The smaller the distance between the objects, the GREATER the force between them.

WHAT IS THE DIFFERENCE BETWEEN INTERMOLECULAR AND INTRA-MOLECULAR FORCES?• Intermolecular forces are formed between molecules and, intra-molecular forces are formed within the molecule.• Intra-molecular forces are much stronger compared to intermolecular forces.• Covalent, ionic, and metallic bonding’s are types of intra-molecular forces. Dipole-dipole, dipole-induced dipole, dispersion forces, hydrogen bonding are some of the examples for intermolecular forces.

BY: AREEBA SALEEM

The set of attractive and repulsive forces that occur between the molecules as a result of the

polarity of the molecules.

INTERMOLECULAR FORCES

When two or more atoms are joined by chemical bonds they form a molecule, electrons travel up to the new molecule and are concentrated in the most electronegativity atom area, the electronegativity is defined as property that have the atoms or molecules to attract electrons. The concentration of electrons in a defined area of the molecule creates a negative charge, while the absence of electrons creates a positive charge.

Intermolecular forces acting between the molecules are classified as:•Permanent dipoles•Induced dipoles•Dispersed dipole.•Hydrogen bondsWithin the 4 groups described above, the most important forces are the top 3, also known as Van der Waals forces.

CLASSIFICATION OF INTERMOLECULAR FORCES

PERMANENT DIPOLESThis type of bonding occurs when two molecules have positive and negative charges, they are polar molecules that have polarity, electrostatically attracting and forming the bond.

INDUCED DIPOLESThis type of bonding occurs when a non polar molecule redistributes the concentration of electrons (it has the ability to polarize) when it approach of a polar molecule, so that it creates a bond between two molecules.In this case the polar molecule induces the creation of the non-polar molecule in a polar molecule.

DISPERSED DIPOLEThis latter case the binding occurs between polar molecules but can be polarized, and when the latter occurs attract each other creating a molecular bond.The binding energies generated by the intermolecular forces are smaller than the energies generated in the chemical bonds, but exist in greater numbers compare with the number of chemical bonds.

Intermolecular Forces: Chemical bonds:

•Intermolecular forces depend on the temperature

•They are weaker than chemical bonds, order of 100 times lower

•The bond distance is at the level of microns

•Unions are not directed.

•Chemical bonds do not depend so much about the temperature.

They are stronger than intermolecular forces

•The bond distance is very small, in terms of Angstroms

•Unions are directed

DIFFERENCE BETWEEN INTERMOLECULAR FORCES AND CHEMICAL BONDS

HYDROGEN BONDINGPRESENTED BY: ZAINAB SOHAIL

A Hydrogen Bonding is a dipole-dipole attractive force that exist between two polar molecules, containing a hydrogen atom covalently bonded to an atom of F, O or N.This attraction between positive hydrogen and negative oxygen or flourine, is called Hydrogen Bond.

HYDROGEN BONDING

• Hydrogen has no inner shell electron and is very small in size, the positive charge density developed is high

• The nucleus of hydrogen atom is exposed to attraction by nearby electron cloud, a lone pair electrons on the electronegative atom

EXAMPLES OF HYDROGEN BONDING

In Proteins:

EFFECTS OF HYDROGEN BONDING

On Boiling point:

bp +78 °C bp -45°C bp -25°C

On Water-solubility:

.………O ̶ H………O ̶ H………O ̶ H…………… ǀ ǀ ↙ ǀ H H R-H H

BY: AISHA AMJAD

DEFINITION:A dipole moment is a measurement of the separation of two oppositely charged .The magnitude is equal to the charge multiplied by the distance between the charges and the direction is from negative charge to positive charge. Dipole moments are a vector quantity.Dipole moments are measured in the SI units Debye which is equal to the of coulomb meters (C m).(1 Debye equals 3.34 x 10-30 coulomb-meters)

DIPOLE-DIPOLE ATTRACTION• Attractive forces that exist

between molecules that have permanent dipoles. • These exist in any polar

substance.•Weaker than Ion-Dipole

force• Increased polarity, stronger

dipole-dipole attraction

H Cl+ -

H Cl+ -

dipole dipole

Attractive force

The dipole–dipole interactions in (a) crystalline CH3CN and (b) liquid CH3CN.

Dipole moments arise from differences in electronegativity. The larger the difference in electronegativity, the larger the dipole moment.

EXAMPLE

POLARITY OF THE DIPOLE MOLECULE:The dipole moment is a measure of the polarity of the molecule.

POLAR MOLECULE.An example of polar molecule is water ,ammonia etc.

For molecules of approximately equal mass and size, the strength of intermolecular attractionsincreases with increasing polarity.

NON POLAR MOLECULE.An example of non polar molecule is carbon dioxide and carbon tetrachloride etc.

VAN DER WAALS FORCES

BY: HAZIQA IFFRIN

• Vander Waals forces are also known as London forces.• They are weak interactions caused by momentary changes in

electron density in a molecule.• They are the only attractive forces present in nonpolar compounds.

Even though CH4 has no net dipole, at any one instant its electron density may not be completely symmetrical, resulting in a temporary dipole. This can induce a temporary dipole in another molecule. The weak interaction of these temporary dipoles constitutes van der Waals forces.

• All compounds exhibit van der Waals forces.• The surface area of a molecule determines the strength

of the van der Waals interactions between molecules. The larger the surface area, the larger the attractive force between two molecules, and the stronger the intermolecular forces.

Surface area and van der Waals forces

• Van der Waals forces are also affected by polarizability.• Polarizability is a measure of how the electron cloud

around an atom responds to changes in its electronic environment.

Larger atoms, like iodine, which have more loosely held valence electrons, are more polarizable than smaller atoms like fluorine, which have more tightly held electrons. Thus, two F2 molecules have little attractive force between them since the electrons are tightly held and temporary dipoles are difficult to induce.

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BY: ASRA FATIMA

APPLICATIONS OF CHEMICAL BONDING

•Today, chemical bonding is understood as the joining of atoms through electromagnetic force. • Not all chemical bonds are created equal: some are weak, and some very strong, a difference that depends primarily on the interactions of electrons between atoms.

• Almost everything a person sees or touches in daily life—the air we breathe, the food we eat, the clothes we wear, and so on—is the result of a chemical bond, or, more accurately, many chemical bonds.

• The strength of chemical bonds varies considerably; there are "strong bonds" such as covalent or ionic bonds and "weak bonds" such as Dipole-dipole interaction, the London dispersion force and hydrogen bonding.