Lewis structures and bonding

Carbon dioxide octet dot cross from wikimedia commons

As a good introduction to bonding, watch this and sing along!

An ion is a charged atom – one that has gained or lost electrons in order to complete it’s outer shell and become stable.  Elements in Group 1 form ions with a charge of +1, since they lose 1 valence electron and end up with one more proton than electron.  Elements in Group 7 form ions with a charge of -1, since they gain 1 valence electron and end up with one more electron than proton.  The bond that is formed when a metal and a non-metal react in this way is called an ionic bond.  In an ionic bond, electrons are donated or received.

Covalent bonds form between non-metal elements.  This could be between the same non-metals (eg. O2) or different non-metals (eg. CO2).  In a covalent bond electrons are shared between the elements to complete the outer shells.  We use Lewis structures to represent this.  Click here for instructions on how to draw Lewis structures (also known as “dot and cross” diagrams).

To practice drawing these diagrams, here are some useful links:-

This site allows you to build your own molecules with single, double and triple covalent bonds.  If you don’t do any others, DO THIS ONE.

This one wold be good for review at the end of the topic.  It generates some multiple choice questions for you to practice identifying the correct Lewis structure.

Finally, this site allows you to construct Lewis diagrams.  It is quite advanced, but some of you might enjoy the challenge 🙂

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