1. Chemical Bonding Presented To: D r. Shabbar Atiq Sb Presented by: Arif Ali MME-12-01 Sarmad Saeed MME-12-02 Muddasar Hussain MME-12-03 M Waqas Liaqat MME-12-04

2. Chemical Bonding ► Chemical compounds are formed by the joining of two or more atoms. ► ► A stable compound occurs when the total energy of the combination has lower energy than the separated atoms.

3. The two extreme cases of chemical bonds are:  Covalent bond: bond in which one or more pairs of electrons are shared by two atoms. Covalent bond Covalent bond  Ionic bond: bond in which one or more electrons from one atom are removed and attached to another atom. Ionic bond Ionic bond

4. Other Types of Bonds Metallic Bonds: In metals all atoms loses their valence electrons which form electronic cloud, which attracts the nucleus of neighboring atoms. Hydrogen Bonding: Electrostatic force of attraction between highly electronegative atom and partially positive hydrogen atom e.g water.

5. Ionic Bond An ionic bond is a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions. Ionic bonds are formed between a cat ion, which is usually a metal, and an anion, which is usually a nonmetal. Example: NaCl forms ionic bond.

6. How are Ionic Bonds Formed? Elements from opposite ends of the periodic table will generally form ionic bonds. Elements from opposite ends of the periodic table will generally form ionic bonds.

7. Properties of Ionic Compounds  Crystalline solids  High melting and boiling points  Conduct electricity when melted  Many soluble in water but not in nonpolar liquid

8. Covalent Bonds bond in which one or more pairs of electrons are shared by two atoms. bond in which one or more pairs of electrons are shared by two atoms. The atoms in covalent bonds do not lose or gain electrons, instead They share pairs of electrons to achieve stability, often by filling their outer energy levels to achieve an octet. Example: N2 forms covalent bond.

9. How are Covalent Bonds Formed? Elements which are close together in electronegativity tend to form covalent bonds and can exist as stable free molecules. Carbon dioxide is a common example.

10. First Subtype of Covalent Bonding  Nonpolar bond  Example: H  Example: H 2  Because both atoms in the H molecule have an equal attraction (or affinity) for electrons, the bonding electrons are equally shared by the two atoms, and a nonpolar covalent bond is formed.  Because both atoms in the H 2 molecule have an equal attraction (or affinity) for electrons, the bonding electrons are equally shared by the two atoms, and a nonpolar covalent bond is formed.

11. Second Subtype of Covalent Bonding Polar Bond formed when electrons are unequally shared between two atoms Example: the hydrogen-oxygen bond in the water molecule.

12. Properties of Covalent Compounds Gases, liquids, or solids Low melting and boiling points Poor electrical conductors in all phases Many soluble in non polar liquids but not in water Are brittle When 2 atoms bond covalently the resulting particle is a molecule

13. Coordinate Covalent Bonds CCCCovalent bonds in which both of the electrons in the shared pair come from the same atom CCCCovalent bonds don’t lose or gain electrons EEEElectrons are not shared equally Example: The bond between NH3 and BF3 is Coordinate Covalent Bonds

14. What Have You Learned? What are the two extreme cases of bonds? What are the two extreme cases of bonds? Do covalent bonds lose or gain electrons? (Yes or No). Do covalent bonds lose or gain electrons? (Yes or No). Why do atoms bond? Why do atoms bond?

15. Any Question ?