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Chemical Bonding

Chemical Bonding. Chemistry Unit 6. EQ . How do atoms make compounds?. Review- Oxidation numbers. Write the Lewis Dot Diagram and give the oxidation number of the following. S O Ca Na P Al. Bonding.

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Chemical Bonding

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  1. Chemical Bonding Chemistry Unit 6

  2. EQ • How do atoms make compounds?

  3. Review- Oxidation numbers • Write the Lewis Dot Diagram and give the oxidation number of the following. • S • O • Ca • Na • P • Al

  4. Bonding • Chemical bond- hold two or more atoms held together to make each have 8 valence electrons • Who they bond with is determined by their oxidation number • Atoms gain, lose, or share electrons to get 8 valence electrons (Octet Rule)

  5. IMPORTANT Compounds are always neutral For ex-NaCl Na = oxidation #= 1+Cl = oxidation # = 1-Total charge on NaCl = 0= neutralFor ex- CaF2Ca= oxidation # = 2+F = oxidation # = 1-F2 = 2-Total charge = 0 = neutral

  6. Types of bonds • Ionic- cation (metal) and anion (nonmetal) bond based on oxidation number; metal loses electrons, nonmetal gains electrons • Covalent- nonmetal and nonmetal share electrons • Metallic- two metals share electrons

  7. Tells about To become

  8. Oxidation numbers of elements can be found by GROUP #s on the periodic table.

  9. Ones and Twos • When do chemical bonds form? • Who is more reactive: alkali metals or alkaline earth metals? • Give the number of valence electrons for oxygen, sulfur, arsenic, phosphorous, and bromine. • Why does calcium form a +2 ion instead of a +3 ion?

  10. For ex- NaCl is made up of 2 elements

  11. Review- Write the answers in your notebook Which of the following compounds are Binary Compounds? KCl H2SO4 CO2 KI PO4 P2O5 CaSO4

  12. Types of Bonds Purpose- to make atoms more stable How e- are distributed determines the type of bond Ionic- electrical attraction b/t cation & anions Covalent- sharing of e- pairs b/t two atoms

  13. Vocab • Cations- positive ions • Anions- negative ions • Electronegativity- the ability of an atom to attract electrons; used to estimate if the bond is ionic or covalent • Diatomic- two of the same (the gases)

  14. Ionic Bonding & Ionic Compounds Chap 8

  15. Basics of Ionic Bonds • Bonding of metal + nonmetal • WS- Types of Chemical bonds • Transfer of electrons • Metal loses e- (cation) nonmetal gains e- (anion) • Ionic charges cancel in the bonding

  16. Formula unit- the smallest formula for an ionic compound • Ex: table salt is composed of lots of atoms, but the formula is written NaCl • The ratio of ions in the formula unit depends upon the oxidation numbers on the atoms

  17. Characteristics of Ionic Bonds • Lattice energy- the energy required to form an ionic compound (bond energy is specific to breaking a bond) • Negative values indicate that energy is released • Positive values indicate that energy is absorbed

  18. Properties of Ionic vs. Molecular Compounds Ionic Molecular *very strong bond b/c very strong attractive force High melting point (do not vaporize at room temp) High boiling point Hard & brittle crystal lattice: ordered repetition of pos & neg charges Good conductors (if they can dissolve in water) Made of metal & nonmetal *Strong bond, but weak attractive force Low melting point (most are gaseous at room temp) Low boiling point Usually a gas at room temp, soft solids, some liquids Poor conductors Made of nonmetals

  19. Polyatomic Ions Polyatomic Ion- a charged group of covalently bonded atoms; covalently bonded, yet behaves like an ion Pg 224 Table 8-6

  20. Summary Answer the EQ- share your answer with the person next to you AFTER you write (that means write THEN talk)

  21. Molecular Compounds Chap 9

  22. Molecule- neutral group of atoms covalently bonded together Molecular compound- many molecules bonded together Electrons are shared b/t atoms in a covalent bond so they all have 8 valence electrons

  23. Lewis structures- demonstrate covalent bonding • Draw the elements symbol • Draw the number of valence electrons

  24. Practice- Lewis Structures • Pg 244 #1-5 • Pg 247 #12

  25. Ionic or Covalent? If two of the same atom are bonded together, then it is completely covalent Nonpolar covalent- bonding e are shared equally; 0-5% ionic character or 0-0.3 EN difference Polar covalent- uneven sharing of e; 5-50% ionic character or 0.3-1.7 EN difference

  26. Naming Molecular Compounds (prefix)1st element + (prefix) root 2nd element Ex. P2O5 diphosphorous pentoxide

  27. # of Atoms Prefix 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca

  28. Ionic or Covalent? • EN values < 1.7 is a covalent bond b/c the bond has 50% or less ionic characteristics • The bond is ionic if the EN difference is > 1.7 Anions attract e- Cations give away e-

  29. Practice • Pg 249 # 13-17

  30. Compare and contrast ionic and covalent bonds

  31. Naming Acids • Oxyacids- contain hydrogen and an oxyanion (PI with oxygen in it) • Replace –ate with –ic • Replace –ite with –ous • Ex. HNO3 nitrate  nitric acid • Binary Acids- contains H and one other element • Hydro + element + ic • Ex. HCl = hydrochloric acid

  32. Practice- Naming Acids • Pg 250 # 18-22

  33. Know the symbols for partial negative charge on the covalent bond (δ-) and partial positive charge (δ+) Know how to tell the bond type based upon EN values

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