Hey! Sign in to get help with your study questionsNew here? Join for free to post
 You are Here: Home

# Why is the relative atomic mass of Chlorine is 35.5

Announcements Posted on
TSR's new app is coming! Sign up here to try it first >> 17-10-2016
1. Yeah, I don't get why.

I've tried searching but I need help.
2. The average mass is 35.5, about half of chlorine atoms have a RAM of 35, the other half 36, same with every other decimal one.
3. Thank the lord
4. (Original post by ProbablyJade)
Thank the lord
ooPS I DIDN'T FNISH THE POST
5. Oh god my reply is a trainwreck
6. What i meant to say was thank the lord my revision could help me qith this question. Basically the value is an average o all the isotopes taking into account the relative abundance
7. Thanks!

Good luck to all tomorrow
8. If a element has more than one isotope the relative atomic mass takes account of the relative abundance and RAM mass of each isotope, for chlorine (I think) about 3/4 is Cl-35 and about 1/4 is Cl-37, giving 35.5 overall, though I very much doubt this is necessary to know. The values will be different for each atom obviously, but that is the general idea.
9. (Original post by Jammy Duel)
The average mass is 35.5, about half of chlorine atoms have a RAM of 35, the other half 36, same with every other decimal one.
That's incorrect mate :/
There are two isotopes of Chlorine. Cl-35 and Cl-37. On average 75% of the atoms are Cl-35 and 25% are Cl-37. Therefore on average the atomic number is 35.5.
35+35+35+37 = 142
142 / 4 = 35.5
10. (Original post by Jono-Wolf)
That's incorrect mate :/
There are two isotopes of Chlorine. Cl-35 and Cl-37. On average 75% of the atoms are Cl-35 and 25% are Cl-37. Therefore on average the atomic number is 35.5.
35+35+35+37 = 142
142 / 4 = 35.5
It's been a while (5 to be precise) but the general point is correct

Posted from TSR Mobile
11. That is the average weighted mass of an atom of chlorine compared to 1/12th the mass of an atom of carbon-12
Spoiler:
Show
My Chem Teacher should be proud I remembered that

Write a reply…

Submit reply

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
that username has been taken, please choose another Forgotten your password?
2. this can't be left blank
this email is already registered. Forgotten your password?
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
your full birthday is required
1. Oops, you need to agree to our Ts&Cs to register
2. Slide to join now Processing…

Updated: June 14, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### How does exam reform affect you?

From GCSE to A level, it's all changing

Poll
Useful resources

## Make your revision easier

Can you help? Study Help unanswered threadsStudy help rules and posting guidelines

## Groups associated with this forum:

View associated groups
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.