Chemical Bonding

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Chemical Bonds
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Chemical BondingWhat holds things together?
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Bonding

• Involves the valence electrons or outermost
  electrons
• Outermost electrons in the last energy shell

How many valence electrons does N have?
Group 5A 5 valence electrons
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Bonding

• Lewis dot structures show the valence electrons
  around at atom and for most molecules and
  compounds a complete octet for the elements

Al
N
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Write out the electron configuration for the
following atoms and ions
He Ne Ar Kr

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NaCl
This is the formation of an ionic bond.
-

Na
Cl
electron transfer
and the formation of ions
Cl2
This is the formation of a covalent bond.
sharing of a pair of electrons
and the formation of molecules
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Ionic Bond

• Between atoms of metals and nonmetals with very
  different electronegativity
• Bond formed by transfer of electrons
• Produce charged ions all states. Conductors and
  have high melting point.
• Examples NaCl, CaCl2, K2O

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Ionic Bonds One Big Greedy Thief Dog!
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1). Ionic bond electron from Na is transferred
to Cl, this causes a charge imbalance in each
atom. The Na becomes (Na) and the Cl becomes
(Cl-), charged particles or ions.
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COVALENT BONDbond formed by the sharing of
electrons
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Covalent Bond

• Between nonmetallic elements of similar
  electronegativity.
• Formed by sharing electron pairs
• Stable non-ionizing particles, they are not
  conductors at any state
• Examples O2, CO2, C2H6, H2O, SiC

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Covalent Bonds
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Chlorine atom 2,8,7
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2 Chlorine atoms Outer shells only
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Chlorine molecule Cl2
Electrons shared
Each outer shell has 8 electrons
Forces (bonds) between atoms in the molecule very
strong
Forces between molecules very weak
Molecular or covalent compounds are usually gases
or liquids they have low melting points and
low boiling points
Molecules have no overall electric charge
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Covalent Bonds Water H2O Methane CH4 Ammonia
NH3 Hydrogen H2 Hydrogen Chloride HCl Oxygen
O2 N.B. Oxygen has a double bond
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Oxygen
Oxygen atom 2,6
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2 Oxygen atoms (outer shells only)
Double covalent bond
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More sharing examples
O2
Share until octet is complete.
N2
octet complete
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Some more sharing examples
NH3
N
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Comparison of Bonding Types
ionic
covalent
ions
molecules
conductive
non- conductive
valence electrons
transfer of electrons
sharing of electrons