ionic-bonds-and-properties-of-ionic
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Transcript ionic-bonds-and-properties-of-ionic
Ionic Bonds and Properties of
Ionic Compounds
Ions
Recall that atoms lose or gain electrons to form ions.
Metals tend to lose electrons and form positively
charged ions called cations.
Nonmetals tend to gain electrons and form negatively
charged particles called anions.
They do this to acquire a stable octet (full outer
energy level – usually 8 valence electrons).
For the representative elements (groups 1,2 &1-17) we
can tell the charge of the ion by the number of
valence electrons. Remember: 1+, 2+, 3+, skip, 3-, 2-, 1-,
zip!
Ionic Compounds
Because opposites attract, cations and anions are
attracted to each other and form neutral compounds
often referred to as salts.
Since the positive and negative charges have to zero
out, the formula for an ionic compound will give the
ratio of each element.
Individual particles of an ionic compound are called
formula units, but they do not exist in isolation. They
form a repeating crystalline structure called a crystal
lattice.
Properties of Ionic Compounds
Let’s fill in the chart!!
Think about it for a minute – what ionic compound
are you very familiar with? Table salt – sodium
chloride. You worked in lab with several other salts.
What state of matter were they all at room
temperature?
If you said solids you are correct!! Now think about
why that might be.
It is because of the strong attractive forces among
the ions and formula units
Melting & Boiling Points
Have you ever tried to melt table salt? If so it probably
didn’t work very well. Why?
Melting and boiling points of ionic compounds are
relatively high. Why?
Those strong bonds that make them solids at room
temperature also require lots of energy to break thus
resulting in high melting and boiling points.
Solubility
Generally when we talk about solubility, we are
referring to solubility in water.
Ionic compounds are usually soluble in water. Why?
Water molecules are polar (we’ll talk more about that
later) and will pull the ions apart.
Response to Stress or Deformation
What does that mean???
Basically it means if you hit it with a hammer, what
happens???
Yep, it crumbles – that’s because ionic compounds
tend to be brittle. Why?
In the crystal lattice, ions have to be lined up with
opposite charges and if that gets shifted, then like
charges repel - it breaks!!
Conductivity
As solids, ionic compounds are not good conductors
of electricity.
However, when dissolved in water or in a molten
state they are good conductors. Why?
In order to move electrons (that’s what an electrical
current is) you need charged particles – in this case
ions- for them to move through. Within the crystal
lattice, there are no loose charged particles for
transferring the electrons!!