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Order of Elements When Writing Out a Compound

Posted: Mon Sep 30, 2019 8:42 pm
by AArmellini_1I
So I know this may seem like a silly question, but honestly my chemistry knowledge is pretty rusty. While working on some homework problems there were multiple times where I solved for the amount (in mols) of each element (which I could do). But what I couldn't figure out was how to write the product based on that information. For example, if you had a mole of Os, 4 moles of C, and 4 moles of O, how do you know that the product is suppose to be arranged as such: OsC4O4? At first I thought maybe it went by alphabetical order but this exampled proved me wrong. And help would be greatly appreciated!

Re: Order of Elements When Writing Out a Compound

Posted: Mon Sep 30, 2019 8:51 pm
by Zaynab Hashm 2I
Typically,if carbon is present it comes first, then hydrogen, and then the others alphabetically. Cations are also written first before anions, so positive before negative in ionic compounds. I believe in the one you mentioned it's C, O, then Os.

Re: Order of Elements When Writing Out a Compound

Posted: Mon Sep 30, 2019 11:20 pm
by Connor Ho 1B
Zaynab Hashm 1C wrote:Typically,if carbon is present it comes first, then hydrogen, and then the others alphabetically. Cations are also written first before anions, so positive before negative in ionic compounds. I believe in the one you mentioned it's C, O, then Os.


I agree. I think it's called the Hill System, where the carbons always come first and then hydrogens and then everything else. So in reality, the compound you're looking at should be C4O4Os.

Re: Order of Elements When Writing Out a Compound

Posted: Tue Oct 01, 2019 7:32 am
by Sara Richmond 2K
I am not sure that the order of the elements will matter too much as professor Lavelle has not reviewed this in class. However, in organic chemistry carbon comes first, followed by hydrogen, followed by oxygen, followed by everything else.

Re: Order of Elements When Writing Out a Compound

Posted: Tue Oct 01, 2019 10:56 pm
by Natalie Wang 1B
I actually asked my TA, and he said that for now, we don't need to know how to write chemical formulas correctly. We also don't need to know how to write out chemical formulas from just the compound's name for our first test! Apparently, we'll be learning the basics of chemical formulas and nomenclature later in the class.

Re: Order of Elements When Writing Out a Compound

Posted: Thu Oct 03, 2019 3:32 pm
by Lizette Noriega 1H
According to the TAs, this information will be given to us. The only situation in which we'll have to write out the compounds will be for questions that include combustion/oxidation/metabolism.

Re: Order of Elements When Writing Out a Compound

Posted: Thu Oct 03, 2019 4:39 pm
by ranqiao1e
Also, I think the order doesn't matter unless the question explicitly asks for it. It's not as strict as the other rules, as long as you can draw the right chemical structure from the formula.

Re: Order of Elements When Writing Out a Compound

Posted: Sun Oct 06, 2019 9:18 pm
by Catherine Daye 1L
I think it's supposed to be in alphabetical order (ex. hydrogen, carbon, chlorine, oxygen). After taking chem for a while and getting used to seeing a bunch of different compounds, putting them in order will become automatic. :)

Re: Order of Elements When Writing Out a Compound

Posted: Sun Oct 06, 2019 11:02 pm
by Lauren Sanchez 3D
I was also a little confused with this topic too, but I was informed that the question itself can present the elements in the correct order already (at least for this first test)