Understanding Chemical Bonds in Compounds

1. Warm-up 3/21/11 • Review questions: List as many elements as you can think of. Then list as many compounds as you can think of. • Teach the teacher questions: If you could start a band what kind of band would you start, what would you call it, and what part would have in it (play guitar, sing, ect.). • Learning Targets: By the end of the class you should know: what happens when elements combine • the two different kinds of bonds • how to balance cations and anions for a chemical bond

2. Chemical Bonds Bonding isn’t just for people.

3. Why do atoms form compounds? • TO BECOME STABLE!! • What does stable mean to an atom? • Full set of valence electrons • Atoms want to have the electron configuration of a noble gas • Atoms will gain, lose or share electrons in order to obtain a full set of valence electrons • Chemical bonding

4. → Combining Elements • The chemical & physical properties of the elements are different than the properties of the compound they make up • Na + Cl2→ NaCl • Reaction of Sodium with Chlorine & Hydrogen with Oxygen

5. Types of Bonds • Ionic Bonds • Contain a metal & a nonmetal (at least 1 of each) • Electrons are gained or lost • Ex. Salt, NaCl • Covalent Bonds • Contain 2 or more nonmetals or hydrogen • Electrons are shared • Ex. Water, H2O

6. Ionic Bonding • In an ionic bond, one atoms gives electrons to another atom. • When atoms combine this way, it is called a formula unit. • Ex. NaCl is a formula unit • The charge of a formula unit is always 0. • The positive and negative charges must always balance each other.

7. Formulas • Chemical Formula—tells what elements a compound contains and the exact number of the atoms of each element. • Ex. NaCl has 1 atom of sodium & 1 atom of chlorine • Ex. H2O has 2 atoms of hydrogen and 1 atom of oxygen. • A subscript (small # written below) is written after a symbol to tell how many atoms of that element are in the compound.

8. Rules for Formulas • Write the cation (metal) first. Write the anion (nonmetal) second. • The net ionic charge is zero. • Use subscripts to indicate multiple ions. • Write the formula unit in the lowest whole number ratio.

9. A trick for formula units • Write both ions with their charges as superscripts. Cu3+ & O2- • Crisscross the charges to make the subscripts in the formula • Do not put + or – in the formula • Cu3+ & O2- Cu2O3

10. Silver Chloride Ag+1 Cl-1 AgCl

11. Zinc Phosphide Zn+2 P-3 Zn3P2

12. Aluminum Oxide Al+3 O-2 Al2O3

13. Warm-Up 3/24/11 • Review: Give an example of a formula unit. • Teach the Teacher: What is the best holiday? Are you going to the pow wow?

14. Flash card • On the front write: • subscript • On the back write: • H2O (submarine)

15. Flash card • On the front: • Ionic Bonding • On the back: • When an element gains or loses an electron

16. Flash Card • On the front: • Covalent bonding • On the back: • When atoms share electrons

17. Warm-Up 3/28/11 • Review questions: What is an ionic bond? (use your flash cards) • Teach the teacher questions: Would you rather be stuck in an elevator with wet dogs or wet cats? • Learning Targets: By the end of the class you should know: polyatomic ions

18. Practice with Chemical Formulas Common Name Chemical Formula Types & Number of Elements involved • Sand SiO2 • Milk of MagnesiaMg(OH)2 • Sucrose C12H22O11 • Vinegar HC2H3O2 • Ethanol C2H5OH →

19. Chemical Bonds • IONIC BONDS • between metals & nonmetals • Electrons form a give take relationship • metals give e- (cation) • nonmetal take e- (anion) • Held together by attraction of opposite charges IONIC ANIMATION Types of Bonds

20. Table Polyatomic Ions PolyatomicIons • The prefix poly- means many in Greek. • ion consisting of a molecule with many covalently bonded atoms • act as a single unit • polyatomic ion is also referred as a radical • Usually end in –ate & –ite • -ide usually indicates binary compounds

21. Oxidation number—the charge of an ion 1+ 2+ 3+ 3- 2- 1-

22. Multiple Oxidation Numbers • Some metals (other metals & transition metals) can have more than 1 oxidation number. • If an element can have more than 1 oxidation number, the charge of the ion is written as a roman numeral in parentheses. • Ex. Copper (I) ion is Cu1+ • Copper (II) ion is Cu2+

23. Roman numerals are not written in the formula • Charges are not written in the formula • Don’t drop polyatomic subscripts • Hydroxide, OH, needs parentheses to indicate multiples. • Cu(II)O CuO • K+1Br-1KBr • CaNO2 Ca(NO3)2 • CaOH2 Ca(OH)2 Mistakes to Avoid

24. Ionic Compounds Group A Elements Write the cation name 1st • Cation name is the same as the element name Write the anion name 2nd • Change the ending of the name to –ide. Rules for Naming

25. Flash Card • On the front write: • Polyatomic Ion • On the back write: • Ion consisting of many covalently bonded atoms

26. WBC • Zinc Fluoride • Zn+2 • F-1

27. WBC • Plumbous Bromide • Pb+2 • Br-1

28. WBC • Stannous Sulfide • Sn+2 • S-2

29. WBC • Silver Phosphide • Ag+1 • P-3

30. WBC • Lead (II) Bromide • Pb+2 • Br-1

31. Warm-Up 3/29/11 • Review questions: What is the subscript in H2O? What are some mistakes to avoid (look at notes)! • Teach the teacher questions: What is one of the better board games? • Learning Targets: Balancing equations and the naming of compounds.

32. Flash Card • On the front write: • Polyatomic Ion • On the back write: • Ion consisting of many covalently bonded atoms (like conjoined twins)

33. Warm-Up 3/31/11 • Review: Why are conjoined twins like polyatomic ions? • Teach the Teacher: What is the best April’s fools prank you have heard of. • Ionic and covalent bonding balancing formula units

34. Flash Card • On the front write: • Molecule • On the back write: • A group of atoms that are bonded together, neutral charge

35. Covalent Bonds • Covalent bonds share electrons • Composed of 2 or more nonmetals (and H) • Covalent compounds are called molecules • Molecules can be polar or nonpolar • Polar molecule—slightly positive and negative at parts—but overall neutral • e- are unevenly shared • Nonpolar molecule—electrons are shared equally—completely neutral

36. Comparing ionic and covelentcompounds

37. Polar or Nonpolar • Polar Bonds • an unequal sharing of the e- • Due to a difference of electro-negativity of the atoms • F is the most electronegative element on PT • Non-polar Bonds • an equal sharing of e- • nonpolar bond animation • Multiple Bonds – More than one pair of electrons can be shared between atoms • Double Bonds = 2 shared pairs of e- • Triple Bonds= 3 shared pairs of e- • Chemical Bonds

38. Naming Covalent Compounds • Mono—1 • Di—2 • Tri—3 • Tetra—4 • Penta—5 • Hexa—6 • Hepta—7 • Octa—8 • Nona—9 • Deca—10 • Use prefixes to tell how many of each element you have. • This is done because you can have different covalent compounds containing the same elements. • Change the ending of the 2nd element to -ide • Ex. N2O is dinitrogen monoxide. • You can leave off the prefix mono- on the first element. • Ex. NO2 is nitrogen dioxide • Not mononitrogen dioxide

39. Formulas for Covalent Compounds • Use the prefixes as the subscript in the formula. • Ex. Phosphorus Trichloride • PCl3 • DinitrogenTetrafluoride • N2F4

40. Covalent or Ionic • Bond between a metal and a nonmetal

41. Covalent or Ionic • Bond between two nonmetals

42. Covalent or Ionic • Can be polar or nonpolar

43. Covalent or Ionic • H20

44. Covalent or Ionic • NH3

45. Covalent or Ionic • NaCl

46. Covalent or Ionic • Roman Numerals are used to indicate the oxidation state of the metalcation

47. Covalent or Ionic • Carbon tetrachloride

48. Covalent or Ionic • Electrons are gained or lost, or transferred from one atom to another

49. Covalent or Ionic • sulfur(VI) oxide

50. Covalent or Ionic • carbon tetrachloride