# What is the percentage of elements in a compound?

• Positronix
In summary, you can use atomic weight ( 232), and not atomic number (the number on the periodic table), to find the percentage of thorium in a compound. The formula is Th02. You can also use this to figure out how much of a compound there is, if you know the atomic weight and the amount of thorium.
Positronix
TL;DR Summary
percentage of elements in a compound without involving molarity?
Thanks in advance for explaining this to me.

I have a very small sample of thorium dioxide in a sealed ampoule (reasonably pure) as an example of thorium for a display.

Every time I wonder what % of the compound is thorium people start talking moles and grams and envisioning it in a solution...

That's great to be able to do all that, and I'll re-acquaint myself with it (I used to do the equations back in college and forgot)
but right off the top of one's head:

Why can't I just say:
the formula for the compound is Th02
1 thorium and 2 oxygens
On the periodic table:
thorium has a mass of 90
oxygen has a mass of 8 (and there's two, so we'll say 8*2=16)

90 / 16 = 5.625
therefore there is 5.625 times as much Th as there is O in ThO2
for %, 100 / 5.625 = 17.778 % Oxygen
100 - 17.778= 82.222% Thorium

and if this is correct, why do I even have to get into molarity for dry weight?
If I have 1 gram of ThO2 why can't I just use the above to say it contains .822 g of Th?

Thanks again.

You need to use atomic weight, (and not atomic number)=thorium is 232. Two oxygens gives 32. The percentage thorium is ## (232/(232+32))100. (This step you did incorrectly in the above). e.g. if there is 4x as much thorium as oxygen, it is then 4/5 thorium and 1/5 oxygen.

symbolipoint
Thanks, I learned 2 important things from your refresher and corrections.
3 things, really -- my silliest error was thinking that a periodic table that was only showing one number (atomic number as it turns out) was showing atomic weight... I hate those! I should have known 90 was too small for Th.

But I realized from your help:
My primary error I'd have continued to make:
I needed to use the whole 232 + 32 for division, not just the larger atom's mass number.
(thanks)

Incidently, bane of my dyslexic existence:
I also (and this gets into my being away from basic math too long with 2x diagnosed dyslexia)
I keep wanting to do extra math because of how my brain works, which just takes longer and opens an extra door for error...

Using ambiguous #'s for demonstration:
If I want to know 3 is what % of 12 (this is easy in its simplicity, but I miss this "shortcut" with larger #'s)
I should not bother to say
12/3 = 4
then
100/4=25
then
25/100=.25

when I can just
3/12=.25 !
for some reason I never intuitively realize I can do this.
My consciousness can fully "see" a 12 is made up of four 3's and 100/4 = 25
but I simply have to memorize that you can always reverse the division to get the % directly.
Conceptually I guess I know division is the counterpart of multiplication...

I'm just trying to beat things into my conscious, intuitive, automatic awareness because, if I wrap my brain around something 360 degrees, it works much better (years from now) than merely memorizing "that's just the way it is". Mere memorization has gotten other people very fasr but I cannot reky on my recall thusly.

If 12/3=4 (and 4 happens to be 25% of 100 because 1/4=.25) then 3/12 will always be .25 !

[100/(12/3)]/100 = 3/12 !

Haha... thanks for helping me get back into the groove.

You helped me 2 if not 3 ways in one, fell swoop.

## 1. What is meant by "% of elements in a compound?"

The "% of elements in a compound" refers to the percentage of each individual element present in a compound. This is determined by dividing the mass of each element in the compound by the total mass of the compound and multiplying by 100.

## 2. How do you calculate the "% of elements in a compound?"

To calculate the "% of elements in a compound," you need to first determine the mass of each element present in the compound. Then, add up the masses of all the elements to get the total mass of the compound. Finally, divide the mass of each element by the total mass of the compound and multiply by 100 to get the percentage.

## 3. Why is it important to know the "% of elements in a compound?"

Knowing the "% of elements in a compound" is important because it helps us understand the composition of the compound and how its properties are affected by the different elements present. It also allows us to accurately predict the behavior of the compound in different conditions.

## 4. Can the "% of elements in a compound" change?

Yes, the "% of elements in a compound" can change. This can happen through chemical reactions, where the elements in the compound may combine with other elements or break apart into different compounds. It can also change through physical processes, such as evaporation or condensation, where the amount of each element present in the compound may change.

## 5. How is the "% of elements in a compound" related to its empirical formula?

The "% of elements in a compound" is directly related to its empirical formula. The empirical formula of a compound shows the simplest ratio of elements present in the compound. This ratio can be converted into percentages, which will give the "% of elements in a compound."

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