Order of Elements When Writing Out a Compound

Science questions not covered in Chem 14A and 14B. Try to limit questions to chemistry (inorganic chemistry, physical chemistry, organic chemistry, biophysical chemistry, biochemistry, materials science, environmental chemistry).

Moderators: Chem_Mod, Chem_Admin

AArmellini_1I
Posts: 107
Joined: Fri Aug 09, 2019 12:15 am

Order of Elements When Writing Out a Compound

Postby AArmellini_1I » Mon Sep 30, 2019 8:42 pm

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!

Zaynab Hashm 2I
Posts: 110
Joined: Wed Sep 11, 2019 12:15 am
Been upvoted: 1 time

Re: Order of Elements When Writing Out a Compound

Postby Zaynab Hashm 2I » Mon Sep 30, 2019 8:51 pm

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.

Connor Ho 1B
Posts: 102
Joined: Sat Aug 17, 2019 12:17 am

Re: Order of Elements When Writing Out a Compound

Postby Connor Ho 1B » Mon Sep 30, 2019 11:20 pm

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.

Sara Richmond 2K
Posts: 110
Joined: Fri Aug 30, 2019 12:16 am

Re: Order of Elements When Writing Out a Compound

Postby Sara Richmond 2K » Tue Oct 01, 2019 7:32 am

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.

Natalie Wang 1B
Posts: 51
Joined: Sat Sep 14, 2019 12:15 am
Been upvoted: 1 time

Re: Order of Elements When Writing Out a Compound

Postby Natalie Wang 1B » Tue Oct 01, 2019 10:56 pm

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.

Lizette Noriega 1H
Posts: 105
Joined: Wed Sep 18, 2019 12:15 am

Re: Order of Elements When Writing Out a Compound

Postby Lizette Noriega 1H » Thu Oct 03, 2019 3:32 pm

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.

ranqiao1e
Posts: 51
Joined: Sat Sep 14, 2019 12:15 am

Re: Order of Elements When Writing Out a Compound

Postby ranqiao1e » Thu Oct 03, 2019 4:39 pm

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.

Catherine Daye 1L
Posts: 104
Joined: Wed Sep 11, 2019 12:16 am

Re: Order of Elements When Writing Out a Compound

Postby Catherine Daye 1L » Sun Oct 06, 2019 9:18 pm

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. :)

Lauren Sanchez 3D
Posts: 52
Joined: Sat Aug 24, 2019 12:17 am

Re: Order of Elements When Writing Out a Compound

Postby Lauren Sanchez 3D » Sun Oct 06, 2019 11:02 pm

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)


Return to “General Science Questions”

Who is online

Users browsing this forum: No registered users and 3 guests