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Compounds and Bonding

Compounds and Bonding. GOAL: You will learn how elements combine to form compounds. Compounds. A compound is formed when two or more elements combine chemically. Elements join together in a way that makes them impossible to separate by physical means.

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Compounds and Bonding

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  1. Compounds and Bonding GOAL: You will learn how elements combine to form compounds

  2. Compounds • A compound is formed when two or more elements combine chemically. Elements join together in a way that makes them impossible to separate by physical means. • Elements in a compound combine in a predictable and definite ratio, based on the combining property of the atoms involved. • NaCl reflects a 1:1 ratio • H2O reflects a 2:1 ratio • CO2 reflects a 1:2 ratio

  3. Chemical Formulas • Chemical formulas are used to represent compounds • Chemical formulas indicate the kind of atoms in a compound • Subscripts are the small numbers in a chemical formula which indicate the particular ratio of atoms in a compound

  4. OxidationNumbers • Is the name given to the combining ability of an atom • Indicates how many electrons an atom gains, loses, or shares in forming a compound • The sum of the oxidation numbers for the atoms in a compound is zero • In order for a compound to exist, it must be electrically neutral

  5. Sodium loses one electron so it has an oxidation number of 1+ Na 1+ Chlorine gains one electron so it has an oxidation number of 1- Cl 1- NaCl This works because 1(1+) + 1(1-) = 0 The sum of the oxidation numbers for the atoms in a compound is zero

  6. Hydrogen loses one electron so it has an oxidation number of 1+ H 1+ Oxygen gains rwo electrons so it has an oxidation number of 2- O 2- H2O This works because 2(1+) + 1(2-) = 0 The sum of the oxidation numbers for the atoms in a compound is zero

  7. Formula Figuring & Writing • The symbol of the metal or the element with the positive oxidation number is written first • The ‘criss-cross’ method is a simple way of determining a formula • The oxidation number of one element becomes the subscript of the other

  8. The formula for the compound composed of potassium and sulfur K 1+ & S 2- The formula for the compound composed of calcium and bromine Ca 2+ & Br 1- ‘Criss - Cross’ Method This becomes K2S This becomes CaBr2

  9. Using Oxidation Numbers, write formulas for the compounds formed from the following elements Sodium & Bromine Potassium & Iodine Calcium & Fluorine Hydrogen & Sulfur Magnesium & Fluorine Lithium & Sulfur ‘Criss-Cross’ Method Practice Remember to check that the sum of the oxidation numbers is equal to zero!

  10. NaBr

  11. KI

  12. CaF2

  13. H2S

  14. MgF2

  15. Li2S

  16. Binary Compounds • Binary Compounds are composed of two elements • Binary Compounds are named beginning with the element with the positive oxidation number • The name of the second element will end in an -ide • NaCl : Sodium Chloride • CaS : Calcium Sulfide • FeO : Iron Oxide

  17. Name each of the following KI FeCl3 Li2S Write formulas for the following: Calcium bromide Potassium oxide Aluminum chloride Binary Compounds Practice

  18. Potassium Iodide

  19. Iron Chloride

  20. Lithium sulfide

  21. CaBr2

  22. K2O

  23. AlCl3

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