Ions
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In general, atoms are electrically
neutral
They have the same number of
protons (+) as electrons (-)
However, because atoms can gain
or lose electrons, they can become
charged.
An atom or a group of atoms that
have gained or lost electrons
(it has a charge)
2 types
CATIONS
(positive ions)
ANIONS
(negative ions)
These atoms lose
electrons
These atoms gain
electrons
Ex. Na1+
Ex. Cl1-
1. IONIC BONDS
– formed between oppositely charged ions
(ex. between a metal and nonmetal)
-forms when electrons are transferred
from one atom to another
Example
Na+1 combined with
Cl-1
NaCl
1st: Na gives up an electron to Cl
2nd: Forming Na+ & Cl3rd: Oppositely charged ions
attract & form a “bond”
NaCl
http://enstrophy.colorado.edu/~mohseni/ASEN5519Spring2004/TypesOfChemicalBonds1.html
http://www.visionlearning.com/library/module_viewer.php?mid=55
Sodium (Na) loses its one
valence electron to Chlorine
(Cl)
resulting in
Na
Cl
A negatively charged Cl ion
(-1)
A positively charged Na ion
(+1)
Na
Cl
1st:
Ca gives up an electron to
each Br
2nd:
Forming Ca2+ & two Br-
3rd:
Oppositely charged ions
attract & form a “bond”
Br -
Ca2+
CaBr2
Br -
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When compounds formed by ionic
bonds are dissolved in water, the
solution will conduct electricity
Why?

Ions in solution are mobile & carry a
charge, therefore can carry an electric
current
2. COVALENT BONDS
-forms when electrons are shared
between the atoms
-formed between two non-metals.
Examples
Cl2
H2
CO
1st:
2nd:
Both Cl have a strong
affinity for their valence
electrons
So both Cl atoms share
a valence electron
3rd: Forming a “bond”
http://enstrophy.colorado.edu/~mohseni/ASEN5519Spring2004/TypesOfChemicalBonds1.html
http://wine1.sb.fsu.edu/chm1045/notes/Bonding/Covalent/Bond04.htm
Cl2 is an example of covalent bonding.
The chlorine atoms each share one of their valence electrons,
Their outermost shell is now full (it is stable)
H2 is another example of covalent bonding.
The hydrogen atoms each share their valence electron with one
another.
Their outermost shell is now full (recall in the first shell there are
only 2 valence electrons!)
1st:
Both C & H have a strong
affinity for their valence
electrons
2nd:
So all atoms share their
valence electron, forming a
“covalent bond”
1st:
Both O & H have a strong
affinity for their valence
electrons
2nd:
So all atoms share their
valence electron, forming a
“covalent bond”
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When compounds formed by
covalent bonds are dissolved in
water, the solution will NOT conduct
electricity
Why?

There are no ions or free charges present,
so no electricity can be conducted
Which of the following compounds
have ionic bonds?
1. MgCl2
2. Al2O3
3. SO2
4. CH4
5. BeF2
6. SiO2
Recall – ionic bonds are
formed between a
metal & non-metal
Which of the following compounds
have covalent bonds?
1. C2H6
2. P2O5
3. NH3
4. Li2S
5. F2
6. AlCl3
Recall – covalent bonds
are formed between
non-metals or
metalloid & non-metal
Which of the following compounds when
dissolved in water will produce an
electrolytic solution?
1. C6H12O6
2. H2S
3. C2H4OH
4. MgCl2
5. AlBr3
Recall – ionic compounds
when dissolved in water
will conduct electricity
Which of the following compounds when
dissolved in water will NOT form ions?
1. Fe2O3
2. H2
3. Ca(OH)2
4. MgS
5. NO2
Recall – only ionic
compounds when
dissolved in water
will form ions
A group of elements bonded together to
form a single ion with their own charge
Same as ions except they are in groups
instead of single atoms
_
OH (hydroxide ion)
•It has a charge of 1•Consists of an oxygen atom and a
hydrogen atom
•Treated like one single ion even though
it is made up of 2 atoms
SO4
2-
(sulfate ion)
•It has a charge of 2•Consists of a sulfur atom and four
oxygen atoms
Charge
on ion
http://www.hcc.mnscu.edu/programs/dept/chem/V.12/page_id_23714.html
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You must memorize the following
names and charges for these
polyatomic ions:
OH-1 Hydroxide
NH4+1 Ammonium
SO4-2 Sulfate
CO3-2 Carbonate
PO4-3 Phosphate
NO3-1 Nitrate
How do we write formulas using
polyatomic ions???
Na1+
Sodium sulfate
SO42-
Na2SO4
1. Treat the polyatomic ion as a single item &
note the charge (sulfate has a charge of 2-)
2. Note the charge on the other element (sodium
(Na) has a charge of 1+)
3. Use the crossover rule to find the formula
(Na2SO4)
Magnesium Hydroxide
Mg2+
OH1-
Mg(OH)2
1. Treat the polyatomic ion as a single item &
note the charge
2. Note the charge on the other element
3. Use the crossover rule to find the formula
Lithium Phosphate
Li+
PO43Li3PO4
1. Treat the polyatomic ion as a single item &
note the charge
2. Note the charge on the other element
3. Use the crossover rule to find the formula
Calcium Carbonate
Ca2+
CO32-
CaCaCO
2(CO3
3 )2
1. Treat the polyatomic ion as a single item &
note the charge
2. Note the charge on the other element
3. Use the crossover rule to find the formula
Ammonium bromide
NH4+
BrNH4Br
1. Treat the polyatomic ion as a single item &
note the charge
2. Note the charge on the other element
3. Use the crossover rule to find the formula
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Worksheet # 1
Study guide, Module 3, page 8 and
9