Order of atoms in molecules

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Ryan Chang 1C
Posts: 105
Joined: Sat Aug 24, 2019 12:17 am

Order of atoms in molecules

Postby Ryan Chang 1C » Sat Oct 05, 2019 3:57 pm

Is there a specific order atoms have to be in? For example, in glucose, how do we know that carbon comes first, then hydrogen, then oxygen.

kevinchang_4I
Posts: 55
Joined: Tue Nov 13, 2018 12:17 am

Re: Order of atoms in molecules

Postby kevinchang_4I » Sat Oct 05, 2019 4:03 pm

Hi Ryan, usually the larger atom will go first, at least that's what my TA said. He also said it is not crucial to know at the moment, and most of the time it is given.

Ami_Pant_4G
Posts: 106
Joined: Sat Aug 24, 2019 12:17 am

Re: Order of atoms in molecules

Postby Ami_Pant_4G » Sat Oct 05, 2019 4:07 pm

After some research, I found out that if carbon is present in the molecule, it is written first. Hydrogen is usually written second, if/when carbon is present. The rest of the elements are written in alphabetical order there after. Despite this, my TA told us that it doesn't really matter right now so I would not worry about it too much. Hope this helps.

preyasikumar_2L
Posts: 101
Joined: Fri Aug 09, 2019 12:17 am

Re: Order of atoms in molecules

Postby preyasikumar_2L » Sat Oct 05, 2019 4:19 pm

It usually doesn't really matter what order the elements are in a compound, as long as the subscripts are correct. According to the Hill system, in compounds with carbon and hydrogen, you typically write carbon first, and then hydrogen, and then the remaining elements in alphabetical order. Another source says that if carbon and hydrogen aren't present, then in ionic compounds write the metal first and then the nonmetal (or cation and then anion), and in molecular compounds write the elements in order of increasing electronegativity. I'm not 100% sure on element order in compound conventions though, but it doesn't matter too much. Hope this helps!

stephaniekim2K
Posts: 79
Joined: Fri Aug 09, 2019 12:16 am

Re: Order of atoms in molecules

Postby stephaniekim2K » Sat Oct 05, 2019 7:36 pm

Like most people said already, the order is not very important, but there is a method called the Hill System that states that Carbon atoms are listed first, then Hydrogen, and the rest of the atoms alphabetically.

ahuang
Posts: 52
Joined: Fri Aug 30, 2019 12:17 am
Been upvoted: 1 time

Re: Order of atoms in molecules

Postby ahuang » Sat Oct 05, 2019 10:29 pm

If carbon is in the molecule, it is usually written first, and hydrogen is second. For now, I think we just need to know that hydrogen and metals come first and nonmetals are second.

rohun2H
Posts: 100
Joined: Wed Sep 18, 2019 12:19 am

Re: Order of atoms in molecules

Postby rohun2H » Sun Oct 06, 2019 4:21 pm

My TA said that it may be ordered in any way and will still be an acceptable answer, at least for now.


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