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Review of Ionic Compounds

Review of Ionic Compounds. In an ionic compound, One element [ non-metal ], can strongly pull electrons away from other element and become a negative ion [a n ion],as the element fills it’s valence shell

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Review of Ionic Compounds

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  1. Review of Ionic Compounds In an ionic compound, • One element [non-metal], can strongly pull electrons away from other element and become a negative ion [anion],as the element fills it’s valence shell • The other element [metal], is weaker at holding it’s electrons and loses valence electrons & becomes a positive ion [cation]. • METAL + NON-METAL

  2. Non-Metal Anions Metal Cations Noble Gases

  3. LESSON 7: MOLECULAR COMPOUNDS Involve only NON METALS bonding with Non Metals H B C N O F Si P S Cl As Se Br Te I At

  4. MOLECULAR COMPOUNDS Both NON METAL elements in a molecular compounds have similar power to pull electrons. So instead of gaining & losing electrons [as in ionic], molecular compounds SHARE electrons between two NON-METAL elements, like a tug of war between two equals.

  5. Sharing Electrons When NON METAL elements share electrons they create COVALENT BONDS – look at the lewis dot structure below for F2

  6. WHY SHARE Electrons? Atoms are most stable when they have a full electron shell. In order to accomplish this, they must share electrons Covalent bonds may be single, double, or triple bonds, depending on the number of electron pairs shared

  7. Sharing Electrons When NON METAL elements share electrons they create COVALENT BONDS This is methane – CH4

  8. NAMING AND FORMULAS: MOLECULAR COMPOUNDS Non Metal + Non Metal Naming molecular compounds is different from ionic, multivalent and polyatomic compounds. In molecular compounds a prefix is used to indicate the numberof each atom present. CO2 C O O  carbon dioxide

  9. Counting Atoms • CaSO4 • Ca S O OOO • Mg3(PO4)2  • Mg MgMgP P O OOOOOOO

  10. MOLECULAR COMPOUNDS • You need to memorize the following prefixes:

  11. MOLECULAR COMPOUNDS • If there is only one of the first element we ignore the prefix, • but if there is only one of the second element we write the prefix – mono .

  12. WRITING FORMULAS • It is important to remember that the prefix indicates number of the element it is attached to. • Molecular compounds do not use the same combining capacities as ionic compounds. • There is NO CRISS CROSS Steps: 1. Write the symbols of the elements • Write the subscript for the number of atoms represented by the prefix. • NO REDUCING dinitrogentetroxide N2O4 [not NO2] Example 1 - sulphur trioxide SO3 Example 2 - diphosphoruspentasulphide P2S5

  13. Practice Questions • carbon dioxide • sulphur hexafluoride • phosphorus trichloride • nitrogen monoxide • CO2 • SF6 • PCl3 • NO

  14. WRITING NAMES • Writing names is also straightforward. You use the appropriate prefix to indicate the number of atoms of that element. Steps: 1. Determine the appropriate prefix for each element. 2. Write the prefix and the name of the element.

  15. Examples • Example 1 - N2O dinitrogenmonoxide • Example 2 - BrI bromine moniodide • Example 3 - XeF4 xenon tetrafluoride

  16. Practice Questions 1. N2O4 2. H2O 3. CF4 4. SO2 5. P2O5 6. NCl3

  17. Answers [* no reducing] • N2O4 • H2O 3. CF4 4. SO2 5. P2O5 6. NCl3 dinitrogen tetroxide* dihydrogen monoxide carbon tetrafluoride sulfur dioxide diphosphorous pentoxide nitrogen trichloride

  18. DIATOMIC ELEMENTS • Some of the elements are gases at room temperature . • Which means they exist naturally as compounds of the same element bonded together. • These elements include: H O N ClF Br I • hydrogen gas H2 • oxygen gas O2 • nitrogen gas N2 • Chlorine gas Cl2 • fluorine gas F2 • Bromine(liquid) Br2 • Iodine(solid) I2

  19. OTHER COMMON NAMES OF COMPOUNDS • O3 - ozone • H2O - water • H2O2 - hydrogen peroxide • NH3 - ammonia • CH4 - methane Lets look at their Electron structures

  20. It is easier to just look at the valence electrons with a lewis dot structure

  21. Combining Capacities of NON-Metals • The number of electrons a non-metal needs to share to become stable is a clue to the number of covalent bonds the element can form • Look to the number of valence electrons and • how many more electrons are needed to achieve a stable valence shell

  22. Table 2: Combining Capacities of NON-Metals

  23. LEWIS DOT STRUCTURESMolecular&ionic compounds

  24. Sharing Electrons When NON METAL elements share electrons they create COVALENT BONDS

  25. Sharing Electrons When NON METAL elements share electrons they create COVALENT BONDS

  26. Lewis Dot for Ionic

  27. HOMEWORK • Textbook – Chapter 4.2 • read pages 152 -157 • do question #1 - 4 Page 156, • pg 158, #1 - 7 • do practice problem on page ?

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