Download Chapter 6 Chemical Bonding

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CHEMISTRY CHAPTER 6
(Chemical Bonding)
A chemical bond is a mutual electrical attraction
between the nuclei and valence electrons of different
atoms that binds the atoms together
Ionic bonding is when bonding results from the electrical
attraction between large numbers of cations and
anions. That is electron transfer results in ionic
bonding
Ex: Na and Cl
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Covalent bonding results from the sharing of electron
pairs between two atoms. That is electron sharing
produces covalent bonding
Ex: water H2O
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How does covalent and ionic bonding differ at the
atomic level?
Ionic bonding:
 An e- is actually transferred from one atom to the other
 This causes the donator to shrink and the acceptor to
enlarge
 The donator becomes (+) and the acceptor (-)
 Structure is held together because of opposites attract
Covalent bonding:
 Electrons are shared between the atoms
 Therefore both atoms will stay the same size
 Atoms are held together not by charge, but merged
orbitals (shared electrons)
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In a non-polar covalent bond the boned electrons are
shared equally by the bonded atoms, resulting in a
balanced distribution of charge
Ex: H-H
In a polar covalent bond the bonded atoms have an
unequal attraction for the shared electrons
Ex: H-F
Polar molecules have an unbalanced distribution of
electrons, thus have two regions of different electric
charges
Ex: Water
Percentage of Ionic character of a bond A-B, X is
electronegativity
XA - XB
% I.C. = ---------------------- * 100%
XA
Ex: Na-Cl What is % ionic character?
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When is a bond covalent or ionic; polar or non-polar
Bonds with more than 50% ionic character are ionic
Bonds with between 5% and 50% ionic character are
polar covalent
Bonds with less than 5% ionic character are
considered to be non-polar covalent
A molecule is a neutral group of atoms that are held
together by covalent bonds
Ex: one water molecule
An chemical formula indicates the relative numbers of
atoms of each kind in a chemical compound by
atomic symbols and numeric subscripts
Ex: Na17Cl17
A Molecular formula shows the types and numbers of
atoms combined in a single molecule of a molecular
compound
Ex: H2O; C2H6
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A diatomic molecules is a molecule containing only two
atoms.
Ex. H2 F2 Cl2 Br2 I2
O
N2
2
Bond energy is the energy required to break chemical
bonds
Ex: Breaking up a H - H bond
Octet Rule: Chemical compounds tend to form so that
each atom, by gaining losing, or sharing electrons,
has an octet of electrons in its highest occupied
energy level.
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Lewis structures are formed when one uses electron dot
notation to form compounds
Ex:
or
or
A single bond is a covalent bond produced by the
sharing of two pairs of electrons between two atoms
Ex: Diatomic Flourine F2
A double covalent bond is a covalent bond produced by
the sharing of one pair of electrons between two
atoms Ex: Calcium Oxide
A triple covalent bond is a covalent bond produced by
the sharing of three pairs of electrons between two
atoms Ex: Ethyne C2H2
Resonance refers to bonding in molecules or ions that
cannot be correctly represented by a single structure.
Ex: sulfur dioxide (SO2)
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A polyatomic ion is a charged group of covalently
bonded atoms
Ex: NH4+ ;
NO3- ;
PO4---
Hydrogen bonding occurs when the inter molecular force
from a bonded hydrogen atom is attracted to and unshared pair of electrons of a nearby molecule.
Ex: Water being drawn to another water
A covalent electron pair is two shared electrons that
forms the bond between two atoms
Ex: water
Further exploration of Bonds
Why is salt (ionic bonds) so brittle?
This is how salt is arranged at the atomic level:
With a closer look we see:
(+) Na's surrounded by (-)Cl's and visa versa
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If for any reason it is unaligned:
How and why does salt dissolve in water?
(at the atomic level)
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 Water is polar (has a +side and a - side)
 This allows the H2O molecules to latch onto and pull apart the Na+
and Cl Eventually their will be no NaCl together (salt all dissolved)