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Chemistry! – Reactions!

Chemistry! – Reactions!. Forming Compounds. When two atoms get close together, their valence electrons interact. Each atom in the compound attempts to have the stable number of valence electrons as the nearest noble gas.

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Chemistry! – Reactions!

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  1. Chemistry! – Reactions!

  2. Forming Compounds • When two atoms get close together, their valence electrons interact. • Each atom in the compound attempts to have the stable number of valence electrons as the nearest noble gas. Metals may lose electrons and non-metals may gain electrons to form an IONIC BOND (IONIC BONDS ONLY OCCUR BETWEEN METALS AND NON-METALS)

  3. Ionic bonds are formed between positive ions and negative ions. • Generally, this is a metal (+) and a non-metal (-) ion. • For example, lithium and oxygen form an ionic bond in the compound Li2O. + Electrons are transferred from the positive ions to negative ions Li+ O2- Li+ lithium oxide, Li2O oxygen lithium See pages 176 - 177 (c) McGraw Hill Ryerson 2007

  4. The Chemical Name and Formula of an Ionic Compound (continued) • Writing formulas for ionic compounds: • In an ionic compound, the positive charges balance out the negative charges. • ***ELECTRONS ARE TRANSFERRED FROM ATOMS. THEY CAN’T BE CREATED OR DESTROYED!**** • The ratio of positive:negative charges gives the proper formula. • The ratio is always written in reduced form.

  5. The Chemical Name and Formula of an Ionic Compound (continued) • For example, what is the formula for magnesium phosphide? • magnesium is Mg2+ phosphorous is P3– • Lowest common multiple of 2 and 3 is 6 • 3 Mg2+ ions and 2 P3– ions • Mg3P2 See page 188 (c) McGraw Hill Ryerson 2007

  6. Formula of an Ionic Compound with a Multivalent Metal For example, what is the formula manganese (III) sulphide? • This manganese is Mn3+. sulfur is S2– See pages 189 - 191 (c) McGraw Hill Ryerson 2007

  7. Formula of an Ionic Compound with a Multivalent Metal For example, what is the formula manganese (III) sulphide? • This manganese is Mn3+. sulfur is S2– • Lowest common multiple of 3 and 2 is 6 • 2 Mn3+ ions and 3 S2– ions (6 electrons) Mn3+ S2– Mn2S3 • Mn2S3 See pages 189 - 191 (c) McGraw Hill Ryerson 2007

  8. Polyatomic Ions • Some ions, called polyatomic ions, are made up of several atoms joined together with bonds. THEY ARE LIKE ONE PACKAGE THAT ALL SHARES THE CHARGE. See pages 192 - 193 (c) McGraw Hill Ryerson 2007

  9. Polyatomic Ions • What is the formula of sodium sulphate? See pages 192 - 193 (c) McGraw Hill Ryerson 2007

  10. Polyatomic Ions • What is the formula of sodium sulphate? Na+ and SO42– Na2SO4 See pages 192 - 193 (c) McGraw Hill Ryerson 2007

  11. Covalent bonds are formed between two or more non-metals. • Electrons are shared between atoms. + Hydrogen fluoride hydrogen electrons are shared fluorine See pages 176 - 177 (c) McGraw Hill Ryerson 2007

  12. Writing and Balancing Chemical Equations • The simplest form of chemical equation is a word equation. • Potassium metal + oxygen gas  potassium oxide See page 206 (c) McGraw Hill Ryerson 2007

  13. Writing and Balancing Chemical Equations • A skeleton equation shows the formulas of the elements/compounds. • A skeleton equation shows atoms, but not quantities of atoms. • K + O2 K2O See page 206 (c) McGraw Hill Ryerson 2007

  14. Writing and Balancing Chemical Equations • A balanced chemical equation shows all atoms and their quantities • Balancing ensures that the number of each atom is the same on both sides of the reaction arrow. • Always use the smallest whole-number ratio. See page 206 (c) McGraw Hill Ryerson 2007

  15. Writing and Balancing Chemical Equations • A balanced chemical equation shows all atoms and their quantities • Balancing ensures that the number of each atom is the same on both sides of the reaction arrow. • Always use the smallest whole-number ratio. Skeleton: K + O2 K2O 4K + O2 2K2O See page 206 (c) McGraw Hill Ryerson 2007

  16. Types of Chemical Reactions:

  17. Factors Affecting the Rate of Chemical Reactions • To make a reaction happen quickly: • Increase the temperature where the reaction occurs • Increase the concentration of reactants • Increase the amount of surface area that reacts • Add a catalyst, or remove an inhibitor

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