Chemical Bonding: Ch. 8

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Chemical Bonding Ch. 8

• Or, what atoms will do to achieve a noble gas
  configuration (stable octet).

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Two ways atoms can achieve stability

• Lose or Gain electrons
• Na 1 (loses 1 electron) Cation
• Cl -1 (gains 1 electron) Anion
• Then the oppositely charged ions attract and you
  get whats called an IONIC BOND.
• Other examples KCl MgO MgCl2
• Composed of a Metal Non-metal !!

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Another way is to share electrons

• Bonds created by sharing are called
• Covalent Bonds
• The electronegativity of the atoms is not strong
  enough to take an electron (cant pay the
  ionization energy).
• Examples HCl H2O CO2
• Composed of two or more Non-metals !!

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Properties of Ionic Bonds

• The stronger of the two. How do we know?
  Melting Pt. of NaCl 801 oC
• Boiling Pt. of H20 100 oC
• Responsible for all the crystals in the world, p.
  218.
• They form very organized shapes called Lattices.
  The energy to break up the Lattice is the Lattice
  Energy.

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Heres a good Deductive Question.

• Page 220
• Why is the Lattice Energy for
• NaCl (769) less than MgO (3795)?
• NaCl- vs. Mg 2O2-
• MgO has the greater /- attraction!
• Oh, I get it !!

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Ionically bonded compounds dissolve in water
nicely.

• Solutions homogenous mixtures
• Ionic compounds like NaCl dissolve in water and
  create solutions called
• ELECTROLYTES
• Electrolytes are solutions that conduct
  electricity !!
• Lets see.

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Lets see if you can answer this!!

• Why is the Melting Point for the compound KF (858
  oC) greater than that of KI (681oC).
• Answer
• What is common between them?
• The valence electron for F is in level 2 for
  I, its level 5 (farther away and easier to
  break the bond!).

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Now, how do you write and name formulas for Ionic
compounds?

• NaCl sodium chloride
• MgO magnesium oxide
• Ca3(PO4)2 calcium phosphate
• Heres the system. We want to be able to write a
  formula for a compound, and then name it. And,
  we want to be able to write a formula from the
  name of a compound.

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Two kinds of Ionic compounds

• Binary ionic made of 2 elements!
• Ternary ionic made of 3 or more!
• Examples
• NaCl MgO Ca3(PO4)2
• binary binary ternary

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Binary

• First write the correct formula by balancing the
  ionic charges!
• Na1 Cl-1 ? NaCl
• Ca2 S-2 ? CaS
• Al3 O-2 ? Al2O3

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Write the Name

• Two Words
• Write the name of the Cation first (always!)
• Write the root of the Anion
• oxygen is ox chlorine is chlor . . .
• End the anion name with the suffix ide
• Ex NaCl is sodium chloride !

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Try these !Write the correct formula and name

• Li O ?
• Ca F ?
• K Cl ?
• Li2O lithium oxide
• CaF2 calcium fluoride
• KCl potassium chloride

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Lets go from the name to the formula!

• Barium sulfide
• Copper(II)chloride
• Iron(III)oxide
• Whats with the Roman Numeral stuff??
• BaS CuCl2 Fe2O3
• Can you figure it out based on the formula??

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The transition elements have more than one
possible charge.

• So, how do we know if Fe (iron) is 2 or 3
• Answer the Roman Numeral
• Old system for these multivalence elements was
  Fe2 ferrous Fe3 ferric
• Sn 2 stannous Sn4 stannic
• Dont panic! The Roman Numeral makes it much
  easier. Iron(II) means Fe2

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Lets try that again!

• Copper(II)chloride
• Zinc fluoride
• Tin(IV)oxide
• CuCl2
• ZnF2
• SnO2

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Do the following on a sheet of paper

• Write the Name
• Li Br
• Ag Cl
• Mg S
• Ca Se
• K Ar
• Fe(III) S

• Write the Formula
• Cesium bromide
• Chromium(III) sulfide
• Lithium iodide
• Barium phosphide
• Aluminum nitride
• Boron oxide