Ionic Compounds

This lesson covers:

  1. The structure of ionic compounds
  2. The properties of ionic compounds
  3. How to work out the formula of an ionic compound

positive / negative / electrostatic / ionic / covalent


Metals normally form ions which have a charge, while non-metals form ions with a charge.


Ions are attracted to other ions with the opposite charge, due to forces. 

positive
negative
electrostatic

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Illustration of a 3D lattice structure of an ionic compound showing ions bonded together.

Ionic structures involve many ions bonded together via bonds. 


The solid arranges itself into a regular 3D structure known as a la.

ionic
ttice

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Select three properties that ionic compounds have:

Conduct electricity when solid

Conduct electricity when liquid

Low melting and boiling points

High melting and boiling points

High strength bonds

Weak strength bonds

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Why can ionic compounds only conduct electricity when in liquid/molten, or aqueous form?

Water is required to conduct electricity 

Solid ionic compounds do not contain charged particles

The negative ions can approach other negative ions

The ions are free to move and carry charge

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Illustration showing a Bunsen burner flame heating a structure of ionic compounds.

strong / weak / high / low / energy / water


Ionic compounds have relatively melting and boiling points. 


This is because ionic bonds are very , and a high amount of is required to break the bonds. 

high
strong
energy

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Illustration showing the structure of an ionic compound with closely packed ions.

Select the correct formula for the ionic compound potassium chloride:

K2Cl

KCl

NaCl

KCl2

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Diagram showing the ionic bonding between magnesium and chloride ions with outermost shells and charges.

Remember that ionic compounds arrange their ions in a way that creates a neutral overall charge. 


For example, magnesium ions have a 2+ charge, while chloride ions have a 1- charge.


Therefore, for every magnesium ion, two chloride ions will be attracted to it, resulting in an overall neutral charge. 

Select the correct formula for a nitrate ion:

NO3+

N3-

NO3-

NO3

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Potassium ions and carbonate ions can form an ionic compound.


Potassium ions have a + charge, while carbonate ions have a - charge. 


This means every carbonate ion will ionically bond with potassium ions.

1
2
2

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What is the chemical formula for the compound calcium sulfate?

Ca2SO4

CaSO4

CaSO42+

Ca(SO4)2

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Make sure you learn the formulae for the following ions:


  1. Hydroxide:  OH-
  2. Sulphate:  SO42-
  3. Nitrate:  NO3-
  4. Carbonate:  CO32-
  5. Ammonium:  NH4+