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So, what makes a bond ionic?
1. Electrons are transferred
2. Usually involves a metal (+) and non-metal (-)
Opposite sides of the table
3. Products are called salts
Ionic compounds are tightly packed together to form ionic crystals
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Positives = Negatives
Strong attraction of positive to negative result in the formation of a crystal lattice
Lattice fence
As a result, ionic compounds have a very high bond strength.
When determining the strength of a bond, scientist look at three things
1. Hardness
2. Melting Point
3. Boiling Point
Hard, Rigid, Brittle Crystalline Structure
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But the structure will break in a characteristic way if a force is applied.
Ionic compounds form hard crystalline structures
Ionic compounds form hard crystalline structures
Hard, Rigid, Brittle Crystalline Structure
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But the structure will break in a characteristic way if a force is applied.
Salt - NaCl
Image from the website:
http://www.soes.soton.ac.uk/resources/collection/minerals/minerals/pages/M12-Halite.htm
www.csuhayward.edu/SCI/sem/back/images/salt1.gif
http://www.dit.ie/DIT/science/chemistry/rsccomp/competition01/hawkesclancy/NaCl.gif
Melting and Boiling Points
The intermolecular forces between ions are strong and require more energy to break.
More Energy = Higher Temperatures Therefore, ionic compounds have
_______ melting and boiling points.High
When ionic compounds are solid…
They are nonconductors of electricity Why?
They are so tightly packed they can’t move.
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Nothing
However, when they are in water (or melt)… The ions separate or dissociate, then they
can move and can carry electricity.
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However, when they are in water (or melt)… The ions separate or dissociate, then they
can move and can carry electricity.
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ZAP!!!
A special name for ionic solutions
Electrolytes are ionic compounds that are dissolved in a medium.
The most common medium
Hint: When you hear Electrolyte, think electricity
- water
Conductivity in Action
Image from the website: http://people.bu.edu/straub/courses/demomaster/electrolytes.html
Water – the medium Sugar – Covalent Bonding
Table Salt – Ionic Bonding
Ionic Bonds are exothermic when they are madeWhen made, they release energy
Energy, usually heat, exits (exo) the system
And it takes energy to break ionic bonds after they are made.
This energy is called the lattice energy.
More about Lattice Energies
The more negative the value, the harder it is to break.
Lattice Energy is affected by: Size of Ions - Smaller ions are harder to
pull apart. Charge of the Ion - greater positive or
negative charges are harder to pull apart.
Size of Ions
Smaller ions have more negative values because their nuclei are closer together and they have more attraction to each other.
Therefore, it is harder to pull apart.
Charge of the Ion
Large positive or negative ions have a more negative lattice energy.
So they are harder to pull apart.
Homework
Page 175: 2, 3, 4, 6 and Page 184: 26 - 29
