Order of Elements in Empirical Formula  [ENDORSED]

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Natalie Noble 1G
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Order of Elements in Empirical Formula

Postby Natalie Noble 1G » Sun Apr 08, 2018 1:56 pm

I understand how to find the ratios of elements for the Empirical Formula but I am having trouble knowing what order to write them in once I get those ratios. I know if carbon is present it goes first and is followed by hydrogen but I don't know if there is a rule to the order of the elements after that. For example during discussion we found the ratios of elements to be 7moles carbon, 8moles hydrogen, 1mol nitrogen, and 1mol oxygen. When writing it out the empirical formula should it be C7H8NO or C7H8ON. What are the rules for the order of elements in a formula?

Fiona Grant 1I
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Re: Order of Elements in Empirical Formula

Postby Fiona Grant 1I » Sun Apr 08, 2018 1:56 pm

I believe that the general rule is that, if there is carbon present in the compound, the order of elements is carbon first, then hydrogen, the the rest of the elements in alphabetical order. If there is no carbon in the compound, then the elements just go in alphabetical order in the formula.

However, there may be special naming rules for different particular scenarios that I am unaware of. I am not sure.

Steve H
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Re: Order of Elements in Empirical Formula

Postby Steve H » Sun Apr 08, 2018 7:28 pm

Why do we have to put the elements in order>?

fara valdez
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Re: Order of Elements in Empirical Formula

Postby fara valdez » Sun Apr 08, 2018 9:07 pm

We put the elements in order due to the fact that for empirical and molecular formulas in chemistry, the Hill System is in place. This states that carbon comes first, then hydrogen, and finally the rest of the elements in alphabetical order. Exceptions to this rule are order of elements in ionic compounds, acids, oxides, and hydroxides.

Garrett Dahn 1I
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Re: Order of Elements in Empirical Formula  [ENDORSED]

Postby Garrett Dahn 1I » Sat Apr 14, 2018 4:48 pm

Be that as it may be, no matter how the elements are arranged in a chemical formula, the actual chemical you are representing will not change. So even though CH2 is the better way to write this formula, H2C means the exact same thing. I don't think we will be expected to exactly know the order of more specific elements, but as some of my peers have stated, Carbon usually seems to come first, followed by Hydrogen.


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