NOTES: Ionic Bonding and Ionic Compounds CH 15

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NOTES Ionic Bonding and Ionic Compounds (CH 15)
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Valence Electrons

• ? Knowing electron configurations is important
  because the number of valence electrons
  determines the chemical properties of an element.
• ? Valence Electrons The e- in the highest
  occupied energy level of an elements atoms.

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Valence Electrons

• ? All elements in a particular group or family
  have the same number of valence electrons (and
  this number is equal to the group number of that
  element)
• Examples
• ? Group 1 elements (Na, K, Li, H) 1 valence e-.
• ? Group 2 elements (Mg, Ca, Be) 2 valence e-.
• ? Group 17 (7A) elements (Cl, F, Br) 7 valence
  e-.

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LEWIS STRUCTURES

• ? Electron dot structures show the valence
  electrons as dots around the elements symbol
• ? Li
• ? B
• ? Si
• ? N
• ? O
• ? F
• ? Ne

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LEWIS STRUCTURES

• ? Electron dot structures show the valence
  electrons as dots around the elements symbol
• ? Li
• ? B
• ? Si
• ? N
• ? O
• ? F
• ? Ne

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Which elements form ionic compounds and which
elements form covalent (molecular)
compounds?? General Rule of Thumb metal
nonmetal IONIC metal polyatomic anion
IONIC polyatomic cation anion
IONIC nonmetal nonmetal(s) COVALENT
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Why are ionic compounds so stable?

• ? IONIC BONDS
• -metal plus a nonmetal
• -cations plus anions
• -opposite charges attract
• ? Examples
• ? Na and Cl- form NaCl
• ? Al3 and Br- form AlBr3

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Ionic Bonds

• Isnt it ionic that opposites attract?

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OCTET RULE

• ? Noble gas atoms are very stable they have
  stable electron configurations. In forming
  compounds, atoms make adjustments to achieve the
  lowest possible (or most stable) energy.
• ? Octet rule atoms react by changing the number
  of electrons so as to acquire the stable electron
  structure of a noble gas.

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Formation of Cations and Anions

• ? can be predicted using the octet rule (not
  always followed, but a good general rule to
  follow for the representative elements)
• -full outer energy level
• -eight electrons (s2p6)
• explains formation of both cations and anions

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CATIONS

• ? Na 1s2 2s2 2p6 3s1
• ? Na
• ? Mg 1s2 2s2 2p6 3s2
• ? Mg2

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CATIONS

• ? Na 1s2 2s2 2p6 3s1
• ? Na 1s2 2s2 2p6
• ? Mg 1s2 2s2 2p6 3s2
• ? Mg2 1s2 2s2 2p6

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OCTET RULE

• ? Atoms of METALS obey this rule by losing
  electrons.
• Na
• Na

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OCTET RULE

• ? Atoms of METALS obey this rule by losing
  electrons.
• Na
• Na

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ANIONS

• ? Cl 1s2 2s2 2p6 3s2 3p5
• ? Cl-
• ? O1s2 2s2 2p4
• ? O2-

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ANIONS

• ? Cl 1s2 2s2 2p6 3s2 3p5
• ? Cl- 1s2 2s2 2p6 3s2 3p6
• ? O 1s2 2s2 2p4
• ? O2- 1s2 2s2 2p6

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OCTET RULE

• ? Atoms of NONMETALS obey this rule by gaining
  electrons.
• Cl
• Cl-

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OCTET RULE

• ? Atoms of NONMETALS obey this rule by gaining
  electrons.
• Cl
• Cl-

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OCTET RULE

• ? Transition metals are exceptions to this rule.
• Example silver (Ag) ? Ag
• By losing one electron, it acquires a relatively
  stable configuration with its 4d sublevel filled
  (pseudo noble-gas)

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OCTET RULE

• ? Transition metals are exceptions to this rule.
• Example silver (Ag) ? Ag
• By losing one electron, it acquires a relatively
  stable configuration with its 4d sublevel filled
  (pseudo noble-gas)

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IONIC BONDS

• ? Anions and cations have opposite charges
• ? Ionic compounds are electrically neutral groups
  of ions joined together by electrostatic forces.
  (also known as salts)
• ? the positive charges of the cations must equal
  the negative charges of the anions.
• ? use electron dot structures to predict the
  ratios in which different cations and anions will
  combine.

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Examples of Ionic Bonds

• Na Cl
• Al Br
• K O
• Mg N
• K P

NaCl- NaCl
Al3Br- AlBr3
KO2- K2O
Mg2N3- Mg3N2
KP3- K3P
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Properties of Ionic Compounds

• ? must contain an ionic bond
• ? crystalline solids at room temperature
• ? ions are arranged in repeating 3-D patterns
• ? high melting point
• ? melted or dissolved in water they conduct
  electricity

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Metallic Bonds

• ? METALS made up of closely packed cations
  surrounded by mobile valence electrons

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Metallic Bonds

• ? METALLIC BOND attraction of free-floating
  (mobile) valence electrons for the positively
  charged metal ions (sea of electrons around the
  cations)
• ? Explains properties of conductivity of
  electricity, malleability, and ductility

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Metallic Properties

• ? CONDUCTIVE can conduct electricity because
  electrons can flow freely in them
• ? DUCTILE can be drawn into wires
• ? MALLEABLE can be hammered or forced into
  different shapes
• WHY??...the sea of free-flowing electrons
  insulates the metal cations from each other so
  they slide easily past one another.

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ALLOYS

• ? most metallic items we use every day are not
  pure metalsthey are ALLOYS.
• ? ALLOYS mixtures composed of 2 or more
  elements, at least one of which is a metal.
• ? prepared by melting a mixture of the
  ingredients together and then cooling

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ALLOYS

• Examples
• ? BRASS Cu Zn
• ? STERLING SILVER Ag Cu
• ? BRONZE Cu Sn
• ? CAST IRON Fe C
• ? STAINLESS STEEL Fe, Cr, C, Ni
• ? SURGICAL STEEL Fe, Cr, Ni, Mo