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Chemical Bonding

Chemical Bonding. Physical Science. Chemical Bonds. When two or more atoms attach to each other, they form a chemical bond Compounds are any two elements chemically bonded Water Sugar Salt And almost all other substances!!!!

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Chemical Bonding

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  1. Chemical Bonding Physical Science

  2. Chemical Bonds • When two or more atoms attach to each other, they form a chemical bond • Compounds are any two elements chemically bonded • Water • Sugar • Salt • And almost all other substances!!!! • Electrons are responsible for the type, strength, and size of a chemical bond

  3. Lewis Structures • Bohr-Rutherford diagrams are large and difficult to show relationships between multiple atoms • Lewis diagrams are used to show multiple atoms • Lewis diagrams show only the valence electrons

  4. Lewis Structures • Valence electrons form the charge of an atom • Electrons are always trying to get together in groups of 8 (forget shells for a minute) • Elements that have 8 valence electrons have FULL outer groups • We call these elements NOBLE or INERT gases, they are found in group 8

  5. Lewis Structures • Label the Nobel (Inert) gases on your chart

  6. Lewis Structures • Elements with 1 valence electron are called the Alkali metals (group 1) (Label)

  7. Lewis Structures • Elements with 2 valence electrons are called the Alkaline Earth metals (group 2) (Label)

  8. Lewis Structures • Elements with 7 valence electrons are called the Halogens (group 7) (Label)

  9. Sy Lewis Structures • Consist of • Element Symbol • Electrons in each open spot

  10. Lewis Structure Lewis Structures 7 • Draw the element symbol • Determine the # valence electrons • Starting at the top, going clockwise, place one electron in each spot around the element symbol Cl

  11. Al Lewis Structure • Draw the Lewis Structure for Aluminum!

  12. 3P 3N - - - Quick Recap! • Draw the Lewis Structure for Lithium! • Draw the Rutherford-Bohr Diagram for Lithium! Li

  13. A note about charges… • Writing a charge • Valence electrons, Bohr-Rutherford, and Lewis diagrams are used to determine charge • Charges are a shortcut to determining bonding properties • RULES OF CHARGE • IF the # of valence electrons is GREATER than 4, the charge is negative (Mostly) • IF the # of valence electrons is less than 4, the charge is positive (Mostly) • Charges are in reference to a full shell of 8

  14. A note about charges… • For example, Aluminum has 3 valance electrons • The possible charges are +3 OR -5 • It either has 3 OVER a full shell, or 5 LESS than a full shell • Because the number 3 is less than 4, we use the charge of +3

  15. Charges • Any element with a charge is called an ION, the charge is an ionic charge • What are the ionic charges of the elements in the table?

  16. Charges

  17. Charges • A few exceptions! • Metals are always a positive charge!! • Non metals are always negative!! • Metalloids can go either way (you are not responsible for choosing – I will tell you) • Example: Boron • According to rule of 4’s….its a +3 charge • But since it’s a nonmetal, we use -5!

  18. Rules of Bonding • All compounds must have neutral charges • (That means the positive charges (cations) and the negative charges (anions) must equal • Subscript numbers are used to show the number of ions • Coefficients are used to show the number of molecules

  19. Rules of Bonding 2H2O Subscript 1 atom of O “1’s” are implied and not written Coefficient Subscript 2 atoms of H

  20. H O H Rules of Bonding H2O

  21. H O Rules of Bonding H2O H

  22. Na Cl Rules of Bonding • Try this one! NaCl (table salt)

  23. Br Br Al Br Rules of Bonding • Last One! Aluminum Bromide

  24. Chemical Bonding • Several Types including • Covalent Bonds* • Ionic Bonds* • Metallic (only between metals)

  25. Covalent Bonds • Electrons are shared between two or more atoms • Covalent bonds can exist between atoms of the same type…for example N-N (N2) or O-O (O2) • Covalent bonds can form single, double, or triple bonds • Covalent bonds are strong and usually result in stable molecules • Carbon always forms covalent bonds and forms the basic molecules for all life substances

  26. Ionic Bonds • Usually formed by members of the Alkali group (ones with +1 electron) • Electrons are donated to another molecule • Between elements from opposite sides of the chart • Forms crystals (salts) & most dissolve in water

  27. Forming Compounds • Write ions with charges • Cross charges • Write subscripts (omit “1’s”) • Use parenthesis if needed

  28. H O H Forming Compounds • What is the molecular formula of water? H+1 O-2 H2O1 H2O

  29. Forming Compounds • What is the molecular formula of carbon dioxide? C+4 O-2 C2O4 Yikes! Reduce like a fraction to lowest denominator ****note**** C2O4 CO2

  30. Forming Compounds • What is the molecular formula of a compound that has aluminum and sulphur? Al+3 S-2 Al2S3 Any guesses on the name? Al2S3

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