Chemical bonds


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Chemical bonds

  1. 1. Chemical Bonds
  2. 2. Sodium Chloride
  3. 3. Chemical BondsTransfer ofelectronsFormed bySharing ofelectronsIonic bondsIonic bonds Covalent bondsCovalent bondsAtoms arejoinedtogetherCOMPOUND
  4. 4. Ionic Bonds Formed through transfer of electrons betweenatoms of metal and non-metal. Example of metals: sodium, magnesium, iron, lead, aluminium Example of non-metals: Chlorine, sulphur, oxygen Metal atoms donate electrons Non-metals atom accept electronsAchievestablestableelectronelectronarrangementarrangementAchievestablestableelectronelectronarrangementarrangement
  5. 5. Ionic BondsNeutralatomDonateselectronsCation(+)Acceptelectronsanion(-)
  6. 6. Formation of Ionic Bonds Ionic compounds Formed through ionic bonds Example 1: sodium chloride Sodium atom: electron arrangement : 2.8.1 Chlorine atom : electron arrangement : 2.8.7
  7. 7. Formation of ionic bonds of insodium chlorideNa ClNa Cl
  8. 8. Formation of ionic bonds insodium chloride Electron arrangement of sodium atom is 2.8.1 A sodium atom donates one electron to achieve the stable octetelectron arrangement (2.8) Sodium ion, Na+is formed This electron is transferred to a chlorine atom with an electronarrangement of 2.8.7 A chlorine atom accepts electron from sodium atom to achieve thestable octet electron arrangement (2.8.8) Chloride ion, Cl-is formed The sodium ion and chloride ion, formed are attracted to oneanother to form a solid sodium chloride, The strong electrostatic force between the ions is called ionic bond(electrovalent bond)
  9. 9. Formation of Ionic Bonds Example 2: magnesium fluorideMgFFMgF F
  10. 10. Formation of ionic compound magnesium fluoride Electron arrangement of magnesium atom is 2.8.2 A magnesium atom donates two electron to achieve the stableoctet electron arrangement (2.8) Magnesium ion, Mg2+is formed This electron is transferred to two fluorine atom with an electronarrangement of 2.7 two fluorine atom accepts 1 electrons each from magnesium atomto achieve the stable octet electron arrangement (2.8) Fluoride ion, F-is formed The magnesium ion and fluoride ions, formed are attracted to oneanother to form a solid magnesium floride, MgF2. The strong electrostatic force between the ions is called ionic bond(electrovalent bond)
  11. 11. Covalent Bondsnon-metal atomsShare electronsStable electronarrangementSingle bondDoublebondTriplebonda pair of electronsis sharedtwo pairs ofelectrons aresharedthree pairs ofelectrons aresharedFormed by
  12. 12. Single Bond Formed when a pair of electrons is shared between 2 atoms. Example : hydrogen molecule Hydrogen atom has 1 valence electron Needs 1 more to achieve duplet electron arrangement 2 hydrogen atoms contribute one electron each for sharing This shared pair of electrons forms a single bond in hydrogenmolecule, H2
  13. 13. Lewis Dot StructureG. N. Lewis 1875-1946
  14. 14. Double Bond 2 pair of electron are sharing between atoms Example: formation of an oxygen molecule, O2 An oxygen atom has 6 valence electron Needs 2 electron to achieve octet electron arrangement 2 oxygen atom each contribute 2 electrons for sharing A double bond is formed between 2 atoms
  15. 15. Triple Bond Is formed when 3 pairs of electron are shared between 2 atoms Example: formation of a nitrogen molecule, N2 Nitrogen atom has the electron arrangement of 2.5. It needs 3 more electron to achieve stable electron arrangement. Each atom contribute 3 electron each Thus sharing 3 pairs of electrons Triple bond is formed between the nitrogen atoms.
  16. 16. Comparison between the ionic bondand covalent bondIonic bond Metal atomsand non-metalatom Transferringelectron Positivelycharged ionand negativelycharged ionCovalent bond Non metalsatoms Sharingelectrons moleculesTypes ofElements involvedin the formationof each bondHow each bondis formedThe particles inthe compoundformed
  17. 17. Try this out!Draw the electron arrangement of the formationfor the following ionic compounds:[Proton number : Li, 3 ; Na, 11 ; K, 19 ; Ca, 20 ;Mg, 12 ; O, 8 ; Cl, 17 ; S, 16] Lithium oxide, Sodium sulphide, Calcium chloride, Magnesium oxide,
  18. 18. Try this out Draw the electron arrangements of theformation Hydrogen chloride Water tetrachloromethane
  19. 19. Try this out Draw the electron arrangements of theformation Carbon dioxide Ammonia (NH3)
  20. 20. The Properties of Ionic andCovalent CompoundsIonic compound Exist as solid High. ->Non-volatile Conduct electricity inaqueoussolution/moltenstate Dissolve in water &do not dissolve inorganic solventsCovalent Compound Exist as solids, liquidor gases Low. ->volatile Do not conductelectricity Dissolve in organicsolvents and do notdissolve in waterPhysical stateat roomtemperatureMelting &boiling pointElectricialconductivitySolubility
  21. 21. Electrical conductivity – ionic compounds Do not conduct electricity in solid. Ions are fixed in positions in the crystal latticestructure Ions do not move freely Conduct electricity in molten or aqueoussolution Ions are free to moveWhy?
  22. 22. Electrical Conductivity – covalent compounds Do not conduct electricity in all states Consist of neutral moleculesWhy?
  23. 23. Melting and Boiling Points Ionic compounds have high melting and boilingpoints. Ions are held together by strong ionic bonds. A lot of energy is needed to overcome the strongelectrostatic forces between the ions Covalent compounds Have low melting and boiling points Consist of molecules that held together by weakintermolecular forces Less heat is required to overcome these forces
  24. 24. Use of covalent compounds Most covalent compounds are good solvents withhigh volatility Example: Alcohol Acetone Ether Hexane Used in Cosmetics Medical industries
  25. 25. The EndGood luck in the exam!