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Warm Up

Warm Up. The atomic mass of an element and the mass number of an atom often have similar values. However, atomic mass and mass number are not the same thing. Explain the difference. Warm Up.

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Warm Up

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  1. Warm Up The atomic mass of an element and the mass number of an atom often have similar values. However, atomic mass and mass number are not the same thing. Explain the difference.

  2. Warm Up Acids and bases are two kinds of chemical compounds. Compare and contrast at least four chemical and physical properties of acids and bases.

  3. Warm Up Why don’t the noble gases in Group 18 on the periodic table form chemical bonds?

  4. Warm Up You measured the mass of a steel pipe before leaving it outdoors. One month later, the pipe had rusted, and its mass had increased. Does this change violate the law of conservation of mass? Explain your answer.

  5. Chemical Bonding Chapter 12

  6. Chemical Bonding • A chemical bondis an interaction that holds two atoms together. • This joining of two atoms is called chemical bonding • Atoms bond by sharing, gaining, or losing electrons • Most atoms bond using only their electrons in the outermost energy level. The electrons in the outermost energy level are called valence electrons Sodium Atom

  7. Octet Rule • The number of valence electrons determines whether an atom will form bonds. • The outermost energy level of an atom is considered to be full if it contains 8 electrons. • Hydrogen and Helium only need 2 valence electrons for a full energy level. How many valence electrons are in the fluorine atom?

  8. Ionic Bonds • Ionic bonds form when electrons are transferred from one atom to another • Ionic bonds form between metals and nonmetals

  9. Covalent Bonds • Covalent bonds are formed when two atoms share one or more pairs of electrons • Covalent bonds form between 2 nonmetals http://www.youtube.com/watch?v=QqjcCvzWwww

  10. Metallic Bonds • Metallic bonds are formed by the attraction between positive metal ions and the electrons in the metal • Electrons are not shared by adjacent atoms (atoms that are next to each other), but are free to “roam” • This gives metals their ability to conduct electricity

  11. SPI 0807.9.10 Identify the reactants and products of a chemical reaction SPI 0807.9.11 Recognize that in a chemical reaction the mass of the reactants is equal to the mass of the products (Law of Conservation of Mass) Chemical Reactions Chapter 13

  12. New Substances • A chemical reaction is a process where one or more substances change to form one or more new substances • During a reaction, bonds are broken, atoms are rearranged, and new bonds are formed • Some signs of chemical reactions: • Gas formation • Solid formation (also called precipitate) • Energy change (light, heat, electricity) • Color change http://www.youtube.com/watch?v=qx5lhj5grts

  13. Chemical Formulas • A chemical formula is a shorthand way to use chemical symbols and numbers to represent a substance • Carbon dioxide = CO2 • Glucose = C6H12O6 The subscript number tells you how many atoms of an element are in the compound

  14. Chemical Formulas • Reading check: What is the difference between CO and Co?

  15. H2SO4 = 2 – hydrogen 1 – Sulfur 4 – Oxygen subscript Subscripts – the number of atoms No number is understood to be “1” Coefficients – the number of molecules 3H2SO4 = H2SO4 H2SO4 H2SO4 6 – H, 3 – S, 12 - 9 coefficient

  16. Chemical Equations • A chemical equation uses chemical symbols and formulas as a shortcut to describe a chemical reaction • The starting materials in a reaction are reactants • The substances formed from a reaction are products C + O2  CO2 What are the reactants and products of the following equation? 2H2 + O2 2H2O The formulas of the reactants are written before the arrow The formulas of the products are written after the arrow The arrow, also called the yields sign, separates the reactants from the products

  17. Law of Conservation of Mass • Law of Conservation of Mass states that mass is neither created nor destroyed in ordinary chemical and physical changes. • This means that a chemical equation must show the same numbers and kinds of atoms on BOTH sides of the arrow!

  18. Law of Conservation of Mass Which chemical equation best shows the law of conservation of mass? • 3Al + 2CuO  Al2O3 + 2Cu • 2Al + 3CuO  Al2O3 + 3Cu

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