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Question about bonding in a level chemistry

How do I determine the amount of lone pairs in an atom quickly in order to draw out its structure?
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Original post by ax4
How do I determine the amount of lone pairs in an atom quickly in order to draw out its structure?


I would say to know its atomic number (so look on your periodic table), and thats how many electrons there are. Each bonding pair has 2 electrons. So if you were looking at NH3 for example. Nitrogen has 5 electrons. N has 3 bonds. One of them is in a bond with a hydrogen. you have 3 of those, so 3 electrons taken up. you are left with 2 electrons. = a lone pair of electrons.
Original post by ax4
How do I determine the amount of lone pairs in an atom quickly in order to draw out its structure?


This is how I teach it: http://www.kentchemistry.com/links/bonding/lewisdotstruct.htm
Original post by ax4
How do I determine the amount of lone pairs in an atom quickly in order to draw out its structure?


E.g ammonia
Number of elec
Group number central atom 5
Bonds to central atom 3
Total 8 =4pair
4pair- 3 bonds = 1 lone pair
If calculating ions add one e- for each negative and subtract 1e- for each positive

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