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Chemical Compounds

Chemical Compounds. Topic 6. Compounds. What is a compound? A group of 2 or more elements It takes on properties different than those of the separate elements that compose it. Ionic and Molecular Compounds. Ionic Compounds Are formed when atoms give/take electrons

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Chemical Compounds

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  1. Chemical Compounds Topic 6

  2. Compounds • What is a compound? • A group of 2 or more elements • It takes on properties different than those of the separate elements that compose it

  3. Ionic and Molecular Compounds • Ionic Compounds • Are formed when atoms give/take electrons • http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/atomic/ionicact.shtml • Molecular Compounds • Are formed when atoms share electrons • http://www.youtube.com/watch?v=yjge1WdCFPs&feature=related • http://www.youtube.com/watch?v=QqjcCvzWwww • We’ll look at Ionic Compounds first

  4. Ionic Compounds

  5. Properties of Ionic Compounds • Formed from metals and non-metals • Forms ions in solutions • Conducts electricity • Solid at room temperature

  6. How Ionic Compounds Are Formed • Once an atom give up electrons, it becomes positive • Once an atom takes electrons, it becomes negative Cl 17p+ Na 11p+ 11 e- 17 e-

  7. Remember… • Positives and negatives attract • Once Na becomes Na+ and Cl becomes Cl- , they are attracted to each other Na+ Cl- 11 p+ 17 p+ 10 e- 18 e- Overall charge +1 -1

  8. Chemical Formulas • Chemical formula – uses symbols and numerals to represent the composition of a pure substance. H2O Symbol for the element oxygen Symbol for the element hydrogen No small number here means 1 atom of oxygen The small number here means 2 atoms of hydrogen

  9. Theory Behind Chemical Formulas CaCl2 1 ion Ca 2 ions Cl each ion is +2 each atom is -1 1 x (+2) = (+2) 2 x (-1) = (-2) (+2) (-2) Overall charge on the compound = 0

  10. How To Write Chemical Formulas Without Acting It Out Or Doing Math • If your periodic table has ion charges listed in the corner, look at the ion charge for each element. Ca+2 and Cl-1 Ca Cl To become… Ca1Cl2  CaCl2 • The superscript should be written as a positive or a negative because the number it’s representing is a number of atoms, not a charge anymore.

  11. Writing Chemical Formulas Example: What is the chemical formula of the product of calcium and chlorine? Note: The superscript shouldn’t be written as a positive or a negative because the number it’s representing is a number of atoms, not a charge anymore.

  12. Naming Ionic Compounds • The name includes both elements in the compound, with the name of the metal first. • The non-metal element is second. Its ending is changed to –ide. Examples: Calcium chloride (instead of Calcium chlorine) Magnesium flouride (instead of magnesium flourine) Sodium iodide (instead of sodium iodine) Zinc sulfide (instead of zinc sulfur)

  13. Polyatomic Ions • Some ions form when certain atoms of elements combine. These ions are called polyatomic ions. (poly- means “many”). • Polyatomic ions are a group of atoms acting as one. • They combine with metals in the same way that a single atom does.

  14. Writing Chemical Formulas With Polyatomic Ions • Chemical formulas are written almost the same as other ionic compounds. • Calcium and nitrate • Ca+2 and NO3- • CaNO3 • Ca(NO3)2  why not just CaNO32? • Differences: Brackets must be written around the polyatomic ion to identify that it is acting as one atom

  15. Naming Compounds With Polyatomic Ions • Naming with a polyatomic ion is very similar to naming compounds between two elements • …but easier • Write the name of the metal, then the name of the polyatomic ion. • Do NOT change the ending of the polyatomic ion • Examples: • Calcium carbonate, sodium nitrate

  16. Multivalent Ions • Some ions have the ability to give up different amounts of electrons which means that they have two possible charges. • Writing formulas with multivalent ions are done just as they were with an ion with only one charge. • Titanium + Oxygen = Ti2O3

  17. Naming Compounds with Multivalent Ions • When writing names with a multivalent ion, you must indicate which version of the element you are using with a roman numeral • (The first listed is always more common) • Example: • Titanium and Oxygen (elements) • Ti+3 and O-2 (ions) • Ti2O3 (chemical formula) • titanium (III) oxide (name)

  18. Just Be Careful When… • Your elements have even numbers of atoms and they have been simplified. • Example: • TiO2 = titanium (IV) oxide • Remember… • Titanium (IV) oxide • Ti+4 and O-2 • Ti2O4 simplified to  TiO2

  19. Practice Time!

  20. Answers

  21. Answers

  22. Molecular Compounds http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/atomic/covalentbond.shtml

  23. Definitions • Molecule • The smallest independent unit of a pure substance and is generally a cluster of atoms joined together. • Diatomic molecules • Molecules made up of two atoms of the same element. • These atoms can never be alone, if they aren’t bonded with another element, they bond with another identical atom. • 7+1 Rule: In the shape of a 7 + Hydrogen on the periodic table • Nitrogen, Oxygen, Flourine Chlorine Bromine Iodine • They create N2, O2, F2, Cl2, Br2, I2, H2

  24. Properties of Molecular Compounds • Composed of two or more non-metals • They can be solids, liquids or gases • They tend to be insulators, or poor conductors • The forces between the molecules are weak bonds • They share electrons

  25. How Molecular Compounds Are Formed • Molecular compounds share electrons instead of transferring them. • Oxygen has 6 valence electrons • Hydrogen has 1 valence electron. • If Oxygen shares electrons with two atoms of hydrogen, oxygen can have 8 electrons and each hydrogen can have 2 electrons – full shells for both • Example: Water

  26. Molecular Compound Examples Diatomic molecule Diatomic molecule

  27. Naming Molecular Formulas • Write the name of the first element. • Change the name of the second element to end with the suffix “ide” • When there is more than one atom in the formula, add a prefix to indicate the number of atoms. Some are listed below. • Exception: When the first element has only one atom, the prefix mono is not used.

  28. Writing Formulas for Molecular Compounds • Unless you’re given the name, writing formulas for molecular compounds are tricky because they don’t deal with charges. • Why don’t they deal with charges? • Because there are no ions (nothing has given or taken electrons). • We won’t deal with writing formulas without the names. Just make sure you can convert the name to the chemical formula and back again.

  29. Drawing Molecular Compounds • Glucose Cocaine Propane • Ethanol Caffeine Acetaminophen

  30. However… • All you’ll have to draw is something like this • NH3 H2 BrO2 H H – H N Br H H O O

  31. Practice Time!!!

  32. Organizing Bonding

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