Let’s start by answering these questions:
What is the maximum number of electrons that can fit in the first shell of an atom?
What is the maximum number of electrons that can fit in the second shell of an atom?
Do all atoms want to have the outer shell completely?
If you answered 2, 8 and full, then you are ready to read on. If not, you have some revision to do before carrying on!
The Chemistry Bar
To explain the difference between these two types of bonding, I would like you to imagine for the next few minutes that you are at the Chemistry Bar.
Everyone that enters the Chemistry Bar is converted into an atom the moment they go inside.
Let’s say that you have now become a non-metal atom with seven electrons in your outer shell and your friend is a metal atom with one electron in his outer shell. You both want to have a full outer shell. What agreement can you come to that allows you to both be ‘happy’?
Your friend can give you one electron so that his inside shell is full, and you will then gain this electron to now have 8 – a full outer shell. You are now both ‘happy’ – or ‘stable’, to be scientifically precise.
When your friend, a metal, gives an electron to a non-metal – you – then this is called an ionic bond. As a result of losing an electron, you friend is now a positive ion. As a result of losing an electron, you are now a positive ion.
The square brackets above show that the ions have now gained a charge. The charge is written in the top right hand corner.
- For each electron gained, the ion gains a 1- charge
- For each electron lost, the ion gains a 1+ charge
- If an ion only gains or loses one electron, you simply write + or – in the top right corner. There is no need to write a 1 in front of it.
- The force between a positive ion and a negative ion is called the electrostatic force of attraction. It is a very strong force.
In a few weeks time you can return to the Chemistry Bar for some more fun. This time make sure you return with a non-metal friend, just like you. Your friend also needs to have 7 electrons in her outer shell, just like you.
You cannot give your friend an electron and be happy as well. This rules out an ionic bond. There must be another way.
There is. You can form a covalent bond. A covalent bond is where two non-metals share electrons between themselves. You can share one of your electrons with your friend, and they can share one of theirs with you. This way, you both ‘feel’ like you have a full outer shell.
Hopefully that answers that question for you!
For an excellent video explanation, please take a look at the video from the guys at Ricochet Science:
See you next week!