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BONDING PART II
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Covalent Bonds
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LET’S FIRST REVIEW IONIC BONDING
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F K In an IONIC bond, electrons are lost or gained,
resulting in the formation of IONS in ionic compounds. F K
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K F
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K F
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K F
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K F
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K F
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K F
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+ _ K F
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K F _ + The compound potassium fluoride
consists of potassium (K+) ions and fluoride (F-) ions
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K F _ + The ionic bond is the attraction between the positive K+ ion
and the negative F- ion
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So what are covalent bonds?
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In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule).
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But rather than losing or gaining electrons,
In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms now share an electron pair.
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The shared electron pair is called a bonding pair
In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms now share an electron pair. The shared electron pair is called a bonding pair
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Chlorine forms a covalent bond with itself Cl2
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How will two chlorine atoms react? Cl Cl
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Cl Cl Each chlorine atom wants to
gain one electron to achieve an octet
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Cl Cl do to achieve an octet? What’s the solution – what can they
Neither atom will give up an electron – chlorine is highly electronegative. What’s the solution – what can they do to achieve an octet?
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Cl Cl
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Cl Cl
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Cl Cl
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Cl Cl
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Cl Cl octet
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Cl Cl octet circle the electrons for each atom that completes
their octets
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Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle circle the electrons for each atom that completes their octets
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Cl Cl The octet is achieved by each atom sharing the
electron pair in the middle circle the electrons for each atom that completes their octets
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Cl Cl This is the bonding pair circle the electrons for
each atom that completes their octets
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Cl Cl It is a single bonding pair circle the electrons for
each atom that completes their octets
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Cl Cl It is called a SINGLE BOND circle the electrons for
each atom that completes their octets
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Single bonds are abbreviated
Cl Cl Single bonds are abbreviated with a dash circle the electrons for each atom that completes their octets
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This is the chlorine molecule,
Cl Cl This is the chlorine molecule, Cl2 circle the electrons for each atom that completes their octets
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O2 Oxygen is also one of the diatomic molecules
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O How will two oxygen atoms bond?
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O Each atom has two unpaired electrons
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O
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O
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O
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O
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O
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O
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O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.
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O Oxygen atoms are highly electronegative.
So both atoms want to gain two electrons.
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O
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O O
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O O
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O O
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Both electron pairs are shared.
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O O 6 valence electrons plus 2 shared electrons = full octet
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O O 6 valence electrons plus 2 shared electrons = full octet
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O O two bonding pairs, making a double bond
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O O = For convenience, the double bond can be shown as two dashes.
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This is the oxygen molecule,
= this is so cool!! This is the oxygen molecule, O2
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Covalent bonding allows for an amazingly large variety
of compounds such as
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water and carbon dioxide,
small compounds like water and carbon dioxide,
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and ethanol (alcohol),
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to larger compounds such as aspirin,
(21 atoms)
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and the sex hormones estradiol and testosterone, (estrogen) (44 atoms)
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to all of the 40,000 proteins you have in your body, including
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insulin, with 779 atoms,
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and hemoglobin, with about 9500 atoms!
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The known chemical world, is far far far below 1% of that.
There are an estimated 1040 possible compounds containing up to 50 atoms The known chemical world, including natural and synthetic compounds, is far far far below 1% of that. NATURE volume 442 p August 2006
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are commercially available.
As of 2007, there are about 31,000,000 known compounds; About 12.5 million of those are commercially available. Thousands of new compounds are discovered or synthesized every week! CAS registry:
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