Asked by Hannie

Helloo.. i got a worksheet about compounds,elements andnumber of elements. it tells me to list the elements and number of atoms found in each of the compounds and i don't understand how to do get the elements and the # of atoms in the equation.. PLease help me..!!!
Common Name- Rubbing alcohol
Compound- C3H7OH
Elements-________
# of atoms of element-___________
Please and Thank You! :)
Answered by DrBob222
The formul for rubbing alcohol (isopropyl alcohol) is C3H7OH.
You have three elements; i.e., C, H, and O. I'm sure that what you are to do is to use a periodic table and find the element and symbol. C is carbon, H is hydrogen, O is oxygen.
How many elements? Look at the subscript (we can't write subscripts but the number following the element is a subscript). In this case, there are 3 C atoms, 8 H atoms (H is written twice, once with 7 and once by itself), and 1 atom of O.
Answered by drwls
The number of different elements is the number of different letters that appear. (Most elements are represented by a pair of letters, only the first of which is capitalized.) In this case, the different elements are C, H and O.

To get the number of atoms, note that there are 3 C atoms, 8 H atoms and one O atom in the formula. Add up those numbers.
Answered by Hannie
Why would you have to add those numbers up?
Answered by drwls
Because the want the number of atoms of ANY type in the C3H7OH molecule.
Answered by Hannie
how would you know how much each is worth? if you look it up in the periodic table.... is it always the same number amount of atoms for the elements?
Answered by Hannie
how would you know how much each is worth? if you look it up in the periodic table.... is it always the same number amount of atoms for the elements?
Answered by drwls
Each atom in the formula counts as an atom, no matter how big it is. If they had asked for the mass of the molecule, then you would treat each one differntly. C weighs 12 times as much as H, for example.

All they asked for was the NUMBER OF ATOMS in the molecule, not the weight or mass of the molecule.
Answered by Hannie
okay. I think I understand it now. Thank you.
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