slide-deck
Properties of giant ionic structures
Structure and bonding
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Properties of giant ionic structures
Structure and bonding
How our teaching resources are designed for the classroom
I can describe the properties of ionic compounds and explain how they result from the ionic structure model.
conductor
charge carrier
solubility
melting point
dissolve
A conductor is a substance that allows charge or energy to flow through it easily due to the presence of delocalised electrons.
Solubility refers to how well a solute is able to dissolve in a solvent to create a solution.
A charge carrier is a particle that enables electrical conductivity, such as delocalised electrons or free–moving ions.
When a substance's particles separate and spread throughout the particles of a solvent resulting in it no longer being seen, it has dissolved.
The melting point of a substance is the temperature at which it changes from solid state to a liquid state.
Changes of state
Solubility
Properties of giant ionic structures
Sodium chloride (table salt) and sodium hydrogen carbonate (baking soda) are both examples of ionic compounds.
Changes of state
table salt, NaCl
At room temperature all ionic compounds:
are in the solid state
do not conduct electricity
baking soda, NaHCO3
In a giant ionic lattice structure, there are strong
electrostatic forces in all directions between oppositely charged ions (ionic bond).
Changes of state
Na+
Cl-
NaCl ions in a 3D lattice
In ionic substances:
the ions are in fixed positions, in the arrangement of a solid
the ions are therefore not free to move and so cannot act as charge carriers and conduct electricity
Ionic compounds in the solid state are good conductors of electricity.
Changes of state
Charge is carried around the circuit by the transferred electrons.
The ions are in a fixed position, so cannot act as charge carriers because they cannot move.
When an ionic compound changes from a solid state
to a liquid state, it melts.
Changes of state
During melting, energy is transferred to the ionic compound by heating.
ions gaining energy during melting
Simulation by PhET Interactive Simulations, University of Colorado Boulder, licensed under CC-BY-4.0 (https://phet.colorado.edu/)
The melting point is the temperature at which the ions change from solid state to a liquid state.
The ions gain energy
which breaks the electrostatic attraction between the oppositely charged ions (ionic bonds) in the lattice structure.
A lot of energy is needed to break the strong ionic bonds between the positively and negatively charged ions in the giant ionic lattice. The ions are then free to move in the liquid state.
Changes of state
Ionic compounds have a high melting point.
When an ionic compound melts and is in the liquid state:
Changes of state
molten ionic compound
containing free moving ions
the liquid can conduct electricity
lit bulb
electrical
circuit
the ions are free to move and act as charge carriers
The melting point of lithium fluoride is high, over 800°C.
Changes of state
It takes a small amount of energy to overcome the strong ionic bonds, so the melting point is high.
It takes a large amount of energy to overcome the strong ionic bonds, so the melting point is high.
When an ionic compound changes from a liquid state
to a gas state, it boils.
Changes of state
Energy is transferred to the molten ionic compound by heating.
The boiling point is the temperature at which the ions change from the liquid state to the gas state.
The ions gain energy and the electrostatic attraction between the oppositely charged ions break.
ions gaining energy during boiling
Simulation by PhET Interactive Simulations, University of Colorado Boulder, licensed under CC-BY-4.0 (https://phet.colorado.edu/)
A lot of energy is needed to break the strong forces of attraction between the positively and negatively charged ions in the liquid state. The ions then have enough energy to be in the gas state.
Changes of state
Ionic compounds have high boiling points.
Here are the boiling points of some ionic compounds.
Which substances are in the gas state at 1500 oC?
Changes of state
sodium chloride 1465 oC
magnesium oxide 3600 oC
copper iodide 1290 oC
calcium carbonate 2850 oC
In terms of particles in an ionic compound and their changes of state, write down the meaning of:
a) melting point b) boiling point
ionic compound
melting point (oC)
boiling point (°C)
Changes of state
What is the state of each compound (i.e. solid, liquid or gas) at:
a) 500 oC b) 750 oC c) 1500 oC d) 3000oC
Give a reason for your answers..
melting point (oC)
boiling point (°C)
2.
3. In terms of structure and bonding, explain
why magnesium oxide has a high melting point of
3600 oC.
4. a) What is an electrical conductor?
b) Why does zinc chloride conduct electricity in the
liquid state but not in the solid state?
Changes of state
In terms of particles in an ionic compound and their changes of state, write down the meaning of:
a) melting point b) boiling point
Changes of state
It is the temperature at which the ions change from the solid state to the liquid state.
b) It is the temperature at which ions change from the liquid state to
the gas state.
2.
Changes of state
What is the state of each compound at:
a) 500 oC b) 750 oC c) 1500 oC d) 3000 oC
a) Both solids, as 500 oC is below both melting points.
b) Copper iodide is liquid, as 750 oC is above its melting point but below its boiling point. Calcium carbonate is solid, as 750 oC is below its melting point.
c) Copper iodide is gas, as 1500 oC is above its boiling point. Calcium carbonate is liquid, as 1500 oC is above its melting point but below its boiling point.
d) Both gases, as 3000 oC is above both boiling points.
3. In terms of structure and bonding explain why magnesium
oxide has a high melting point of 3600 oC.
Changes of state
4. a) What is an electrical conductor?
An electrical conductor is a substance that allows charge to flow through it easily.
Magnesium oxide has a giant lattice structure.
There are very strong electrostatic forces of attraction (ionic bonds) between the positively charged magnesium ions and negatively charged oxide ions.
A lot of energy is needed to break the strong ionic bonds between the oppositely charged ions; so that they can move and take on the arrangement in a liquid.
4. b) Why does zinc chloride conduct electricity in the liquid
state but not in the solid state?
Changes of state
In solid zinc chloride:
the zinc and chloride ions are in fixed positions in the giant lattice structure
the ions are not free to move
so the ions cannot act as charge carriers
therefore zinc chloride cannot conduct electricity.
In liquid zinc chloride:
the zinc and chloride ions are free to move
therefore the ions can act as charge carriers
so liquid zinc chloride can conduct electricity.
Changes of state
Solubility
Properties of giant ionic structures
Most ionic substances can dissolve in water.
Water is the solvent. They are soluble in water.
Solubility
sodium chloride dissolving in water
The solid can no longer be seen, a solution has been formed.
Solubility
a salt dissolving in water
A substance dissolves when its particles separate and spread throughout the particles of a solvent resulting in it no longer being seen.
Simulation by PhET Interactive Simulations, University of Colorado Boulder, licensed under CC-BY-4.0 (https://phet.colorado.edu/)
Ionic compounds are soluble in water:
Solubility
sodium chloride solution
water molecules are attracted to the ions in the lattice
the ionic forces of attraction are overcome and the substance dissolves
water molecule (H2O)
Which diagram shows potassium bromide solution?
Solubility
The solubility of an ionic compound in water indicates how well it dissolves at a particular temperature.
Solubility
Lithium chloride is much more soluble in water than sodium or potassium chloride as a maximum of 83.5 g of solid lithium chloride can dissolve in 100 g of water at 20 oC.
Which ionic compound is the most soluble in water?
Solubility
magnesium chloride 56.0 g/100g H2O
potassium chloride 34.0 g/100g H2O
sodium fluoride 4.0 g/100g H2O
calcium nitrate 129 g/100g H2O
When an ionic compound dissolves in water the ions are free to move around the solution:
Solubility
ionic compound solution
the solution can conduct electricity
lit bulb
electrical circuit
the ions can act as charge carriers
Copper chloride solution can conduct electricity.
Solubility
In a solution the ions are not in a fixed position and cannot act as charge carriers.
In a solution the ions are free to move and act as charge carriers.
Draw a line from the property to its explanation.
Solubility
most ionic compounds are soluble in water
no charged particles are free to move
bonds are weak
charged ions are free to move
electrons are free to move
bonds are strong
water molecules are attracted to ions and the ionic forces of attraction are overcome
ionic compounds conduct electricity when dissolved in water
Draw a line from the property to its explanation.
Solubility
most ionic compounds are soluble in water
no charged particles are free to move
bonds are weak
charged ions are free to move
electrons are free to move
bonds are strong
water molecules are attracted to ions and the ionic forces of attraction are overcome
ionic compounds conduct electricity when dissolved in water
2. a) Write down the meaning of solubility.
b) List the ionic compounds in order of decreasing solubility.
Task B
c) In terms of structure and bonding, explain why most ionic
compounds will dissolve in water?
Solubility
3. a) Label the diagram showing the particles in sodium chloride
solution.
b) Explain why sodium chloride solution can conduct electricity.
Solubility
__________
__________
__________
2. a) Write down the meaning of solubility.
b) List the compounds in order of decreasing solubility.
Solubility
It is the ability of a substance to dissolve in a particular solvent creating a solution. It tells us how well a solute dissolves in a solvent at a particular temperature.
lithium chloride
potassium nitrate
copper sulfate
calcium carbonate
Solubility
c) In terms of structure and bonding, explain why most ionic compounds dissolve in water?
Ionic compounds have a giant lattice structure.
There are very strong electrostatic forces of attraction (ionic bonds) between the positively charged ions and negatively charged ions.
The water molecules are attracted to the ions in the lattice.
The strong electrostatic forces of attraction are broken and the substance dissolves.
3. a) Label the diagram showing the particles in sodium chloride
solution.
b) Explain why sodium chloride solution can conduct electricity.
Solubility
Na+ ion or sodium ion
Cl- ion or chloride ion
water molecule
The ions are free to move and can act as charge carriers.
In a giant ionic structure, there are strong electrostatic
forces in all directions between oppositely charged particles.
Properties of giant ionic structures
Ionic compounds have high melting points and high boiling points because strong ionic bonds need a lot of energy to be broken.
Most ionic substances can dissolve in water.
The ions of ionic compound dissolved in water are free to move around and the solution can conduct electricity.
The ions of ionic compounds that are in the liquid state are free to move around and the liquid can conduct electricity.
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