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April 30 Day 6

April 30 Day 6. DRQ: What is an ion? Activities: DRQ/Review DRQ Review Test Chapter 11 Introduction Homework: Complete Why Atoms Combine Cornell Notes pages 298 -302. Chapter 11. Chemical Bonds Pages 296-321. Introduction to Chemical Bonds pg 297. Chemical Bonds

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April 30 Day 6

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  1. April 30 Day 6 DRQ: What is an ion? Activities: • DRQ/Review DRQ • Review Test • Chapter 11 Introduction Homework: Complete Why Atoms Combine Cornell Notes pages 298 -302

  2. Chapter 11 Chemical Bonds Pages 296-321

  3. Introduction to Chemical Bonds pg 297 • Chemical Bonds • The explosion of fireworks are chemical changes in which chemical bonds are broken • When a chemical bond is broken, energy is usually released • The explosion happens when substances in fireworks combine (bond) with oxygen in the atmosphere • These combinations happen because the electrons in atoms can be given away or borrowed. • Remember, chemistry is all about electrons, the nucleus of an atom will rarely change – that is called radioactivity.

  4. Fireworks! • Today's fireworks rely on black powder for two critical functions. • Gas released when the powder combusts first propels the firework skyward (Newton’s third law of motion) • Later the black powder inside blasts its contents outward into the patterns that spectators come to see. • However, other chemical ingredients are also needed; without them fireworks would produce little more than yellowish-orange sparks and white smoke. • Here is how they make those great colors…

  5. Chapter 11 Chemical BondsSection 1: Why Atoms Combine Pages 298-302 • Words to know: • Chemical Formula • Chemically Stable • Chemical Bond • Objectives/Study Questions • Describe how a compound differs from the elements that compose it. • Explain what a chemical formula represents. • State a reason why chemical bonding occurs.

  6. 11.1 Summary • Compounds have different properties than their elements. When a bond forms, the properties change. • Remember Na (highly reactive metal) and Cl (poisonous green gas) combine to NaCl (edible crystalline solid, dissolves in H2O) • H is a light flammable gas, O is also a flammable gas, add two H to an O and you get a clear, colorless liquid. • A chemical formula tells you what elements make up the compound and in what ratio. • H2O has two atoms of H for every one atom of O • NaCl has one atom of Na for every one atom of Cl • A Chemical bond is how atoms share, lose or gain electrons that will help them become more stable. It joins two atoms together. • Na is highly reactive, so is Cl, when they bond with each other, they are less reactive.

  7. Some bonding background info… • Atoms with a full outer energy level are chemically stable – they will not react with another atom to form a new substance • Which elements are these? • For most atoms, this means it has 8 outer electrons. • This is called the octet rule • For H and He what should this rule be called?

  8. More bonding background… • Most metals have 3 or fewer outer electrons and tend to lose electrons to form positive ions. • These will react with negative ions to form new compounds • Most non metals have 5 or more outer electrons and tend to gain electrons to form negative ions. • These will react with positive ions to form new compounds.

  9. Cornell Notes pages 298-302 • Take notes on: • Compounds • Formulas • See examples of these on page 300 • Chemically stable atoms • Make sure you draw some examples of Dot diagrams

  10. May 1 Day 1 DRQ: Why do atoms combine? Activities: • DRQ/Review DRQ (check homework completion) • Review Notes for 11.1 • Section Wrap up page 302 Homework: Complete Section Wrap up

  11. Compounds • Most matter is a compound or a mixture of compounds • A compound has different physical properties than the elements that combined to form the compound. • The physical properties of the elements are gone, they are replaced by the physical properties of the new compound. • Na (highly reactive metal) and Cl (poisonous green gas) combine to NaCl (edible crystalline solid that dissolves in H2O) • H is a light flammable gas, O is also a flammable gas, add two H to an O and you get a clear, colorless liquid. Check out this clip…

  12. Formulas • Formulas are made up of chemical symbols. • This is a shorthand way of naming the atoms in a compound • What is the formula for Water? • What does the formula mean? • A subscript is a number “written below” and after the chemical symbol. • The subscript tells how many atoms of that element are in the compound • Fe2O3 has two Iron atoms chemically combined with three Oxygen atoms

  13. Chemical Formula • The chemical formula for any compound tells • What elements it contains • The ratio of the atoms of those elements. • Look at table 11-1 on page 300. • What elements are in each compound? What is the ratio of atoms in each compound?

  14. Chemically Stable Atoms • Most elements form compounds because it makes them chemically stable. • An atom is chemically stable if its outer energy level is filled with electrons • A dot diagram is used to quickly show how many outer level electrons an atom has. • In this video you’ll see how two Cl atoms SHARE two valence electrons. • It also shows the use of dot diagrams to indicate the electrons in the outer energy level and how they are shared in a bond. • This type of bond is called covalent.

  15. Chemical Bonds • A chemical bond is a force that holds the atoms in a substance together. • You just saw how two Cl atoms can share electrons to create a bond. • Here is how a chemical bond forms between Mg and O • When Mg and O become bonded, each Mg loses two electrons and each O gains two electrons. • The bond forms because Mg has 2 extra + charges and the O has 2 extra – charges and they are attracted to each other. • This video segment should help you visualize this process.

  16. Valence Electrons • As you saw in the videos, for most elements the outer energy level (valence) is most stable when it contains eight electrons. • Why would Krypton be considered chemically stable? • Why is H so unstable?

  17. Outer Levels:Giving, Stealing and Sharing • Atoms that do not have eight outer level electrons will bond with atoms of other elements to fill an octet (eight electrons) • They do this by gaining, losing or sharing electrons • What happens to an atom if it loses an electron? • What happens to an atom if it gains an electron? • When atoms SHARE electrons they have to be close enough that their electron clouds intermingle.

  18. Complete the Section Wrap-up Page 302Questions 1-4 and the Skill BuilderANSWER 1 and 3 IN FULL SENTENCES! • What happens to the properties of elements when atoms form compounds? The property of elements… • Write formulas for • A compound with one calcium atom and two fluorine atoms • A compound with two aluminum atoms and three sulfur atoms • Why do most elements tend to form compounds? Most elements tend to form compounds to/because • The label on a box of washing soda states that it contains Na2CO3. • Name the elements in the compound. • In what ratio are the elements present?

  19. Skill Builder • Look at Table 11-1 on page 300. There are two kinds of chemicals in this table, organic and inorganic. Chemicals with Carbon in them are considered organic. Carbon is an amazing element. It can form one, two, three and even four bonds. Check out this video. See if notice anything about the bonds they show…

  20. Re-create this table • Organize it by the type of compound, Organic or Inorganic. • Hint (there are three organic compounds and six inorganic compounds)

  21. Not Done? • Finish these questions for homework. • You will find them on page 302 of your textbook.

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