Ionic Compounds & Molecules
The way elements combine
Elements  Compounds
• When you add more than one element
together, you get a compound.
• Compounds are pure.
• They are broken apart again in chemical
reactions.
• What are some compounds you are
already familiar with?
– H2O
– NaCl
- CO2
- C6H12O6
- H2O2
Ions
• An ion is an atom or a
group of atoms that
has an electric
charge.
• They have the charge
because they either
lost or gained an
electron(s).
Ions
• If an atom loses an electron, it has a
positive charge.
• For example: Li+, Na+, K+, NH4+, Ca2+
• If an atom gains an electron, it has a
negative charge.
• For example: F-, Cl-, I-, HCO3-, NO3-, O2-
• Notice, sometimes the numbers are below
(subscript) and sometimes they are above
(superscript). This means different things.
Ionic Bonds
• An ionic bond is the
attraction between two
oppositely charged ions.
• When you add a positive
ion to a negative ion you
usually get a ionic
compound.
• The compound’s charges
cancel and make it
neutral.
Ionic Compounds
• When two oppositely charged ions attract,
you get an ionic compound.
• (Write the electron dot diagrams for Na, Mg, and Cl)
• Some examples
are:
..
- = NaCl
[Na]+ + [:Cl:]
..
..
..
- + [Mg]2+ + [:Cl:] - = MgCl
[:Cl:]
2
..
..
Naming Ions
• The name of the positive ion comes first,
followed by the negative ions.
• If the negative ion is a single element, the name
ends in –ide.
• If the negative ion is polyatomic (more than one
atom), the name ends in –ate or – ite.
• Example: NaCl- Sodium Chloride
MgO – Magnesium Oxide
K2SO4 – Potassium Sulfate
Properties of Ionic Compounds
• In general, Ionic compounds are:
– Combination of metal + non metal
– Many are solid at room temperature
– Hard, brittle crystals
– High melting points and boiling points
– If dissolved in water they conduct electricity
due to strong charges
Covalent Bonds
• Covalent bonds are a different type of
bond than ionic bonds.
• When atoms share their electrons rather
than gain or lose them, you get a covalent
bond.
• The force holding the atoms together is
the attraction of each atom’s nucleus for
the shared electrons.
Molecules
• A molecule is a compound composed of
atoms that are sharing electrons in a
covalent bond.
• (Write the electron dot diagrams for O, C, and N)
• Some
examples
are:
..
..
.. ..
. . .
.O .+ .O .= O O =
. .. . .. .
..
..
O2
O + C + O = O C O = CO2
N + N = N N = N2
Some Funny Molecules
More Funny Molecules
Polar Molecules
• Sometimes the nucleus of one atom pulls
more strongly on the electrons than the
nucleus of the atom it is sharing with. This
unequal sharing of electrons is called a
polar bond.
• As a result, the electrons are pulled
slightly closer to one atom than the other
which causes the molecule to have slight
electrical charges.
What Polar Molecules?
• One of the most common polar molecules
is water.
• The strong polarity of water is what makes
it “stick” together seemingly
Polar Water
Naming Molecules
• Naming of molecules is different from
naming ionic compounds.
• Often times Latin prefixes are used.
• One = mono
Two= di
• Three = tri
Four = tetra
• Five = penta
Six = hexa
• Seven = hepta
Eight = octa
• Nine = nona
Ten = deca
Naming Molecules
•
Compound
Systematic name
•
•
•
•
•
•
•
•
•
•
•
•
•
NF3
NO
NO2
N2O
N2O4
PCl5
SF6
S2F10
H2O
H2S
NH3
N2H4
PH3
nitrogen trifluoride
nitrogen monoxide
nitric oxide
nitrogen dioxide
dinitrogen monoxide
laughing gas
dinitrogen tetraoxide
phosphorous pentachloride
sulfur hexafluoride
disulfur decafluoride
dihydrogen monoxide
water
dihydrogen monosulfide hydrogen sulfide
nitrogen trihydride
ammonia
dinitrogen tetrahydride
hydrazine
phosphorous trihydride
phosphine
Common name
Some Irregular Molecules
• Irregular names are often
that way because they
were named prior to the
system being in place
and the names stuck.
• CH4
• C6H6
• C2H6
• C2O2H4
• H2O
Properties of Molecules
• In general, molecules are usually:
– The combination of a non-metal + non-metal
– Many are liquid or gas at room temperature
– Lower melting and boiling points than ionic
compounds (because of less strong attraction
for each other).
– When dissolved in water, they do not conduct
electricity.
Ionic Bantering
• I just lost an electron.
Are you sure?
Yes, I'm positive.
• You need to keep and ion people who make jokes like that.
• So true. I could be negative and moan about it, but he is a bright
spark, with an electrifying whit. Not too sure if those in-charge feel
the same.
• OK, so I'm no comic. I should have stayed static and realised my
potential in my own field.
• Perhaps we should conduct ourselves away from the current
discussion.
• There may be some resistance to that suggestion.
• This is all too shocking.
• Are you serious? Because people who can be serious now and then
tend to show increased potential.
• If this surge of replies continues, i fear i may blow a fuse.