Ionic bonding (AQA GCSE Chemistry): Revision Notes
Ionic bonding
Ionic bonds are powerful chemical connections that happen when metals meet non-metals. These bonds create many important compounds we see every day, like salt and other minerals.
Ionic compounds are everywhere in our daily lives! Common table salt (sodium chloride), the calcium in our bones (calcium phosphate), and even the fluoride in toothpaste are all examples of ionic compounds.
What are ionic bonds?
When a metal atom comes close to a non-metal atom, something interesting happens. The metal gives away some of its electrons to the non-metal. This creates two charged particles called ions, which then attract each other strongly.
Think of it like this: metals are generous with their electrons, whilst non-metals are happy to accept them. This electron transfer creates a strong electrostatic attraction between the oppositely charged ions.
How positive ions form
Metal atoms have a special property - they easily lose electrons from their outer shell. When they do this, they become positive ions (also called cations).
Here's what happens:
- Sodium atoms lose 1 electron to become ions
- Magnesium atoms lose 2 electrons to become ions
- The lost electrons leave the metal with more protons than electrons, making it positive
This process helps metals achieve a stable electronic structure, just like the nearest noble gas.
How negative ions form
Non-metal atoms work differently. They prefer to gain electrons to fill up their outer shell. When they gain electrons, they become negative ions (also called anions).
For example:
- Chlorine atoms gain 1 electron to become ions
- Oxygen atoms gain 2 electrons to become ions
- The extra electrons give non-metals more electrons than protons, making them negative
Why ions are stable
All ions try to get the same electron arrangement as noble gases. Noble gases are very stable because they have complete outer shells - usually 8 electrons (except helium which has 2).
When atoms become ions, they achieve this stable "noble gas structure". This drive to achieve a stable electron configuration is the fundamental reason why ionic bonding happens so easily and why these bonds are so strong.
Patterns in the periodic table
The periodic table helps us predict what ions will form:
Understanding Group Patterns:
The position of an element in the periodic table directly tells us how many electrons it will gain or lose to achieve a stable structure.
Metals:
- Group 1 metals lose 1 electron → form 1+ ions
- Group 2 metals lose 2 electrons → form 2+ ions
Non-metals:
- Group 6 non-metals gain 2 electrons → form 2- ions
- Group 7 non-metals gain 1 electron → form 1- ions
This pattern makes it easier to work out chemical formulas. For example, sodium (Group 1) and chlorine (Group 7) make , whilst magnesium (Group 2) and oxygen (Group 6) make .
Electron transfer in action
Worked Example: Magnesium and Oxygen Ionic Bonding
Let's trace through exactly how magnesium and oxygen form ionic bonds:
Step 1: Magnesium atom has 2 electrons in its outer shell Step 2: Oxygen atom has 6 electrons in its outer shell Step 3: Magnesium gives its 2 outer electrons to oxygen Step 4: Magnesium becomes (positive ion) Step 5: Oxygen becomes (negative ion) Step 6: The opposite charges attract, forming an ionic bond
Result: The compound formed is (magnesium oxide)
Key Points to Remember:
- Ionic bonds form when metals react with non-metals
- Metals lose electrons to become positive ions
- Non-metals gain electrons to become negative ions
- All ions try to get a stable noble gas structure
- Group position tells us what charge an ion will have