Covalent bonding

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Lecture 17

• Covalent bonding

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Dan Gable
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During his prep and college careers, Gable
compiled a record of 182-1 - he was undefeated in
64 prep matches and was 118-1 at Iowa St.
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Quote"Im a big believer in starting with high
standards and raising them. We make progress only
when we push ourselves to the highest level. If
we dont progress, we backslide into bad habits,
laziness and poor attitude."
Establish a great goal
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At Waterloo West High School, Gable went 64-0,
with 25 pins

• Establish a concrete specific goal

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Hand back papers

• Email progress reports

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Go over quiz from last time

• Go over quiz as worksheet for gen Chem

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Check homeworkand give home work

• Ten factor labeling problems - ion sheet

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Who has personal chemistry number between 1 and 10

• Webb and who

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We have been discussing how an atom will gain or
lose an electron so that it acquires a noble gas
configuration
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Last time we talked about naming writing and
constructing formula units
Copper (II) Sulfate
SnCl2
FeCl3
Sodium Oxide
KOH
Ammonium hydroxide
CuO
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Once this Ion is formed the ions combine to form
ionic compound in a ratio that will yield a
neutral ionic compound
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Is there any other way for an unstable atom to
gain stability other than gaining or losing an
electron?

• Yes!!!!!!!

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Man in the back of a truck and electron
Drop the tool box
Pick up another tool box to gain balance
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Sharing of electrons
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Sharing electrons to establish an octet

• Two beach balls that together will achieve a
  mutual

octet
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Exhausted guys trying to walk

• What if one is tall and one is short??
• What if they are the same size??

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Unstable neutral hydrogen atom
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Combining of valence shells
Covalent bond
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Co valent

• Co operation
• Co habitate
• Co educational
• Co valent

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Bonds

• Stabilizing charged ions by establishing ionic
  bonds creating stable mass of ions called
• ionic compound
• Stabilizing neutral atoms by establishing
  covalent bonds creating stable mass called
  molecules

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Ionic compounds metalsnonmetals
Typically

• Covalent
• Nonmetal
• Nonmetal

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Covalent bonds occur when two nonmetals (two
takers) wrestle over an electron

• Both elements are takers and neither is strong
  enough to pull off an electron off the other and
  thus it is a tug o war for the electron

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How strong is not strong enough

• To quantitate the strength Linus Pauling used his
  Electronegativity numbers

Remember that Electronegativity is the same as
ionization numbers Except that electronegativity
is quantitative with numbers from .7 to 4
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For an electron to be completely pulled off there
must be a difference of Electronegativity of
About 2.1
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Na Cl
K O
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If the Electronegativity is from 0 to .5 then
the molecular orbital is balanced with even
sharing
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If the Electronegativity difference is from .5
to 2.1 then the molecular orbital is skewed
toward the more electronegative
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If the Electronegativity is from 2.1 or greater
then the molecular orbital is broken and the
electron is displaced creating ions
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With HCl the shared electron is pulled toward
the more attractive atom.

• H 2.0 .
• Cl 3.2 difference of 1.2

  This is called a Dipole
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The dipole exists because there is a pulling in
of the electrons orbit on one side of the
molecule and an exposed nucleus on the other
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The covalent bond that causes two regions of
charge is called a polar covalent bond

• Nonpolar covalent bond is when the two share the
  electrons equally.

Such as in what covalent molecules?
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Sharing of electrons in water
Notice how the electrons are pulled to the oxygen
nucleus
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This is what gives water its polar nature the
unbalanced sharing of electrons between oxygen
and Hydrogen
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The Molecular orbital is the space within which
the electrons orbit
With water the molecular orbital is pulled toward
the oxygen
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So in order to be stable and atom will either1)
lose or gain an electron2) share an
electron a) balanced shareing is
nonpolar b) unbalanced sharing polar
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Ionic compoundMetal and nonmetalgiver and
takerionic

• Molecule
• Taker and taker
• Nonmetal and Nonmetal
• covalent

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Molecules are of a specific size and held
together by covalent bond
DNA Sugar polymers H2 O2
protein

• Ionic compounds are held together by ionic bonds
  and described by empirical formulas

Salt HCl
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There is a special class of molecules that are
very common and very powerful

• If you share an electron you want to share
  equally so there is a balanced sharing.

The most equal would be two of the same
elements!!!!
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Diatomic Molecules

• HOFBrINCl

These elements never exist alone but because of
the electrons shell they create strong diatomic
covalent bonds.
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Oxygen has 6 valance electrons It needs to share
2 electrons to gain an octet
Bonding of oxygen atoms by sharing 2 electrons
O2
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So compounds are either going to clump as ions
like Na Cl-or

• They will share their valance electron shell and
  intimately associate in what is called a covalent
  association called a covalent bond.

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Covalently bonded compounds are called molecules.

• How many individual elements are in a ionic
  compound?
• How many elements are in a molecule.

H2O CO2
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Molecules are a neutrally covalently bonded
group of atoms that act as a unit
H2O C6H12O6 CO H2CO3 DNA
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The intermolecular covalent bond is very close
and very tight