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Chemical Bonding

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Published in: Chemistry
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This presentation describes the Ionic Bonding in which the student will understand the following: To describe lattice structure of NaCl To describe Covalent bond To use dot – and – cross diagram To describe Metallic bonding

Athumani R / Dubai

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Qualification: Bachelor Of Pharmacy

Teaches: Others, Biology, Chemistry, Physics

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  1. CHEMICAL BONDING AND STRUCTURE Prepared by: Athumani Kawambwa (Bpharm) Muhimbili University - Tanzania
  2. Learning Outcomes To describe Ionic Bonding To describe Lattice structure of NaCl To describe Covalent bond To use dot — and — cross diagram To describe Metallic bonding
  3. + To describe shape and bond angles in molecules and ions. To describe intermolecular forces. To describe Hydrogen bond. + To describe and explain anomalous properties of water To deduce types of bonding present in a molecule
  4. IONIC BONDING Ionic compounds They are crystalline solids with high melting points. They conduct electricity with decomposition at electrodes in molten or aqueous solution They are hard and brittle with easily cleave or break crystals They are soluble in water.
  5. Ionic Bonding •:• Ionic bonding results from electrostatic attraction between oppositely charged ions. Example: Sodium Chloride (NaCl), has electrostatic force of attraction between positively charged Sodium (Na+) and negatively charged Chlorine (Cl-). The ions are arranged in crystal lattice, which determines the shape of crystal.
  6. Sodium Chloride Sodium Chloride present in sea water and the crystals of salt are readily obtained from partial evaporation of sea water in the salt pan. Most of other minerals are found as well- formed crystals. Examples: - Aluminium Oxide - Sodium Iodide
  7. GENERAL FEATURES OF IONIC COMPOUNDS 1. They have higher Melting Point. The higher melting points of ionic compounds is very useful in our dily life. Example 1: Aluminium Oxide (A1202) whose melting point is 2345 K ( which is equal to 2072 oc). A fibers form of Aluminium Oxide is used in tiles on space shuttle for protection from high temperature on re-entry into the atmosphere.
  8. 2. They conduct electricity in molten or aqueous form. The ionic compounds conduct electricity in molten form, a process called ELECTROLYSIS *Electrolysis is a useful process in the following aspects:- a). Production of Chlorine from Concentrated aqueous Sodium Chloride (Brine). b). Production of Aluminium from the aqueous Aluminium Oxide.
  9. ELECTROLYSIS In electrolysis ionic compound is broken down into ions namely CATIONS and ANIONS. Strong Ionic compound is broken down completely by the passage of Electricity, and is termed as STRONG ELECTROLYTE. Example: Sodium Chloride (NaCl) Weak Electrolyte is broken down partially by the passage of Electricity , and is termed as WEAK ELECTROLYTE. Example: Sodium Ethanoate
  10. CATIONS They are positively charged ions During electrolysis Cations migrate to negative electrode. • This negative electrode is also called CATHODE The cations are from Metals. Examples of Cations are:- Sodium ion (Na+) Magnesium ion (Mg2+) Aluminium ion (A13+)
  11. The positive ions gain electrons to become Metals Examples: For Sodium ion (aq) For Copper ion Cu2+ + 2e (aq) Cucs) —The number of electrons gained by cations depend on the magnitude of charge of that Cation.
  12. ANIONS *They are negatively charged ions During electrolysis Cations migrate to positive electrode. This positive electrode is also called ANODE The anions are from Non Metals. Examples of Anions are:- Chloride ion (Cl-) Sulfide ion (S 2 — ) Oxide ion (02-)
  13. The negative ions lose electrons to become Non Metals Examples: For Chloride ion 2C1- (aq) For Oxide ion 202 (aq) C12(g) + 2e 202@) —The number of electrons to be lost by anions depend on the magnitude of charge of that Anion.
  14. Question 1: Write the ionic half equation for electrolysis of Copper (Il) Chloride ANSWER Copper (Il) Chloride is CuC12 In Electrolysis it will decompose to Copper ion (Cu2+) and Chloride ion At Cathode (aq) At Anode Cucs) 2c1- + 2e (aq)
  15. Write the ionic half equation for electrolysis of Aluminium Oxide ANSWER Aluminium Oxide is A1203 In Electrolysis it will decompose to Aluminium ion (A13+) and Oxide ion (02-) At Cathode 2A13+ (aq) At Anode 302 (aq) 2A1(s) 302 (g) + 6e
  16. FORMATION OF IONS FROM ELEMENTS Positive ions/ Cations are formed when electrons are removed from atoms. • This occur easily in Metals Negative ions/ Anions are formed when electrons are gained by atoms This occurs easily in Non Metals. Hence, when Metals and Non Metals combine, electrons are transferred from metals to non metals
  17. Metals will lose all it's outer electrons from it's shell to become stable. *Non metals will gain the electrons from metals to become stable. *Ionic bonding results from the Electrostatic attraction between Oppositely charged ions. *Both Metals and Non Metals will be stable by those movable electrons.
  18. We use dot-and-cross diagram to show electronic configuration of elements and ions. The electrons of one element in the compound are shown by dots, and those of second element are shown by cross In dot-and-cross diagram inner electrons are omitted. The circle is drawn round the outer shell electrons
  19. + The nucleus of an element is shown by symbol of that element. The dot-and-cross diagram for an ions is placed in a square brackets with charges outside the brackets. The electrons are placed in pairs in the shell for clarity.
  20. Dot-and-Cross diagram of Sodium Chloride
  21. TRENDS IN MELTING POINTS OF IONIC COMPOUNDS The melting point of ionic compounds increases as the charges on ions increase. Therefore • Mg2+ has higher melting point than Na A13+ has higher melting point than Ca2+
  22. GEMSTONES ..... ..... ......... Gemstone and other semi-precious stones, such as Emeralds, Sapphires, and Rubies are ionic compounds valued for their colour and hardness *Gemstones are crystalline and are cut so that they sparkle light. They are cut by exploiting the cleavage planes between layers of ions in the crystal structure.
  23. THE TRENDS: SOLUBILITY OF IONIC COMPOUNDS IN WATER Ionic compounds can dissolve in water. Metal nitrates and most metal chlorides are soluble in water, as almost all of the Group I metals such as Potassium Chloride (KCI) Sodium Chloride (NaCl)
  24. CHARGES OF IONIC COMPOUNDS DETERMINE ITS EXTENT OF SOLUBILITY The ionic compounds that carry higher charges tend to be less soluble or insoluble in water. Group I hydroxides such as NaOH, KOH are soluble in water. Group Il hydroxides and Group Ill hydroxide are sparingly or insoluble in water
  25. When ionic compounds dissolve in water, there are some energy should be provided to overcome the strong attractive forces that occur in hydrated ions. In hydrated ions, water molecules are attracted to either anion or cation by strong electrostatic force. Oxygen atom of water is attracted by positively charged ion. Hydrogen atom of water is attracted by negatively charged ion. This is possible because water molecules are polar
  26. + Electrolysis of ionic compounds can occur only when ions are free to move. In the lattice the ions are fixed in position they do not move. That's why the ionic compounds do no conduct electricity when in solid form. When ionic compound is melted or dissolved in water, the ions are no longer fixed in position so they are free to move, and hence they can conduct electricity.
  27. REFERENCES • AS Level and A Level Chemistry Brian Ratcliff et el 10th Edition Online Verified Sources
  28. NEXT PART COVALENT BONDING THANK YOU FOR YOUR COOPERATION

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