Chelsea12345
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Question 5 - part a on this:
https://pmt.physicsandmathstutor.com...%20A-level.pdf

How do i work out the bond angle?
The mark scheme says the answer is 94-105.5 degrees?
From the structure i have drawn, there's two bonding pairs and one lone pair? so a bond angle for a bent molecule should be given?
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BobbJo
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there are 2 lone pairs on O and 2 bond pairs around O so bent geometry and bond angle about 104.5 which is in the range of the ms
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username1445490
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You need to be able to calculate number of lone and bonded pairs.

1. For the central atom - what group is it in? This is the number of electrons in its outer (valence) shell.
2.Each single covalent bond adds an electron to the number obtained in 1.
3. Take the total number of electrons obtained by doing 1 and 2 (this MUST be an even number) and divide it by 2. This is the total number of pairs around the central atom.
4. Count how many bonds there are - this is the number of bonded pairs and the rest are lone pairs.

eg for H2O2

1. O is in group 6 so has 6 electrons.
2. There are 2 covalent bonds from the O so that is 2 more electrons.
3. Total number of electrons = 6+2 = 8. Divide by 2 = 4 pairs.
4. There are 2 single bonds so 2 bonded pairs and therefore 2 lone pairs.

Bond angle for 2 bonded and 2 lone pairs = 104.5. V-shaped, bent, non-linear.

If the species is an ion and has a -1 charge then add one more electron to the total and is it is +1 then deduct one electron from the total.
Last edited by username1445490; 1 year ago
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