A_-_102_F11_Notes

Forexampleinonemoleculeofmethanech4oneatomofcarbonshar

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Unformatted text preview: 
compound
have
the
same
proportion
by
mass
of
the
constituent
 elements.
 ChE102
Fall
2011
Class
Notes
‐
Introduction
 A ‐1 
 Isotopes
 • All
atoms
of
the
same
element
have
the
same
number
of
protons,
but
they
may
have
 different
numbers
of
neutrons.

 • Atomic
number
is
what
controls
most
of
the
properties
of
the
atom
 • For
example,
chlorine
always
has
17
protons
but
it
commonly
has
either
18
or
20
 neutrons.
 • Therefore,
there
are
two
isotopes
of
chlorine,
both
with
atomic
number
17
but
 having
mass
numbers
of
35
and
37.
 
 
 Ions
 Atom
is
neutral
and
has
the
same
number
of
protons
(positive
charge)
as
electrons
 (negative
charge)
 Ion
is
an
atom
that
has
gained
electrons
(____________
=
negative
charge)
or
lost
electrons
 (______________
=
positive
charge)
 • Therefore,
an
ion
has
a
charge
 For
example:

 
 
 Chemical
Bonding
 • Minimal
knowledge
required
for
this
course:
 • Elements
combine
to
form
compounds
by
bonding
 • Bonding
involves
electrons
 • In
a
covalent
bond,
one
or
more
atoms
share
one
or
more
electrons.
 • For
example,
in
one
molecule
of
methane
(CH4),
one
atom
of
carbon
shares
 electrons
with
four
atoms
of
hydrogen
 
 • In
an
ionic
bond,
one
atom
donates
one
or
more
electrons
to
another
atom:
 • For
example,
in
sodium
chloride
the
sodium
Na
donates
an
electron,
becoming
Na+
 • The
chlorine
accepts
it,
becoming
Cl–
 • The
formula
for
sodium
chloride
isNaCl,
but
it
does
not
exist
as
a
molecule.
 Instead,
it
forms
an
ordered
crystal
of
alternating
Na+
and
Cl–
ions.
 
 
 Polyatomic
Ions
...
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