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Covalent Bond

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Published in: Chemistry
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This presentation describes the covalent bond and examples of covalent bond molecules.

Athumani R / Dubai

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Qualification: Bachelor Of Pharmacy

Teaches: Others, Biology, Chemistry, Physics

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  1. COVALENT BONDING PREPARED BY: ATHUMANI R KAWAMBWA PHARMICIST (BPHARM)
  2. OUTLINE Covalent bonding Lone Pairs
  3. Covalent compounds Many are liquids or gases or solids with low melting points and boiling points. Examples: Water *Ammonia *Methane Ethanol Sucrose and Polyethene
  4. Covalent compounds have different properties compared to ionic compounds. The covalent compounds contain molecules in which groups of atoms are held together by covalent bonds. Covalent compounds are non conductors of electricity, and they are insoluble in water. They may dissolve in organic solvents such as Ethanol and Cyclopentane.
  5. Some crystalline covalent compounds are very hard, they have high melting and boiling point and are more difficult to cleave than ionic compounds. Such covalent compounds also contain covalent bonds, which extended throughout the crystal in a giant lattice structure. Example: Quartz Crystals
  6. MODE OF ARRANGEMENT OF ATOMS IN A QUARTZ LATTICE
  7. In a covalent compounds the molecules have bonding electrons which are now in a molecular orbital rather than atomic orbitals. The molecular orbitals may be considered to arise from the overlap of atomic orbitals. *Molecular orbitals are labelled using Greek letters, which are: Sigma o Pie Tt Delta 6 These are parallel labels for atomic orbitals s, p, d, etc.
  8. Single covalent bond consists of sigma orbital and is called sigma bond (o). The sigma bond (0— bond) in the hydrogen molecules
  9. The pie (n) orbitals are found as pie bonds (n — bond). A double covalent bond consists of sigma bond and a pie bond. Single line is used for single bond. Double lines are used for double bonds. Each covalent bond is a shared pair of electrons.
  10. The following are dot-and-cross diagrams for some covalent compounds. a. Methane Or Brown methane x
  11. b. Water o
  12. c. Chlorine
  13. H d. Ammonia N H Search inside Image
  14. e. Ethene
  15. f. Carbon dioxide
  16. SILICON HEXAFLUORIDE Silicon hexafluoride (SF6) is used as insulator in large electrical transformers but it is largely replaced by Polychlorinated Biphenyls (PCBs), which were found to cause environmental damage. Silicon hexafluoride (SF6) has more electrons in its outermost shells. The sulfur atom in SF6 has more electrons in its most outermost shell than the next noble gas, Argon. When Chemist realized that is possible for atoms to expand their outer shell in this way.
  17. It wa suggested that noble gases thought to be unreactive, might form compounds in that way. BORON TRIFLUORIDE Boron trifluoride (BF3) is an example of molecule in which atom has not achieved noble gas electronic configuration its outermost shell.
  18. LONE PAIRS Lone pairs These are pairs of outermost shell electrons in atom that do not involve in covalent bonding. These are non bonding electron pairs. In ammonia, nitrogen has one lone pair. Sometimes these lone pairs are used to form a covalent bond to an atom that can accommodate two further electrons in its outermost shell.
  19. Example: When Ammonia and Hydrogen ion combine to form Ammonium ion (NH4 ).
  20. + The covalent bond from nitrogen atom to the H + ion is formed by sharing lone pairs of electrons from the nitrogen. As both electrons come from nitrogen this type of bond is called Dative covalent bond. The word dative comes from Latin word that means Give Dative covalent bonds are represented by arrows as displayed formulae of molecules. *Dative covalent bonds are also called Coordinate bonds in metal complexes.
  21. Further examples of dative covalent bond is Aluminium chloride ALUMINIUM CHLORIDE When solid Aluminium chloride is heated, it becomes vapour at 180 0 C. The vapour consists A12C16 molecule.
  22. THE STRUCTURE OF A12C16 Cl
  23. Two Chlorine atoms, each donates a lone pair of electrons to vacant orbitals of Aluminium atoms. Electronic configuration of Aluminum atom Al = [Ne]Ü vacant orbitals Vacant/empty orbitals to accept lone pairs of electrons
  24. QUESTIONS 1. Water molecule will hydrate the aqueous hydrogen ion to form oxonium ion, H30+. Draw a cross-and-dot diagram and displayed structure for oxonium ion. 2. Draw a dot-and-cross structure of carbon dioxide.
  25. 3. BF3 forms a white solid when reacts with the gaseous ammonia. A bond formed between Boron and Nitrogen. The formula of the solid is F3BNH3. Draw a dot-and-cross structure and displayed formula of this products.
  26. NEXT SUBTOPIC BONDS OF INTERMEDIATE CHARACTERS
  27. REFERENCES •AS Level and A Level Chemistry Brian Ratcliff et el 10th Edition Online Verified Sources

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