View source for Information in chemical formulae

A chemical formula tells us:

* [[#Number ratio of the atoms|the number ratio of all the different atoms in the chemical formula]].
* [[#Number ratio of the ions|the number ratio of the ions in the chemical formula]].

==Number ratio of the atoms==
A chemical formula gives the number ratio of the different kinds of atoms present in the compound. This means that the ratios are the same if you count in individual atoms, dozens of atoms, or moles of atoms. 

Take a look at the ratio of the number of atoms in sodium carbonate, Na<sub>2</sub>CO<sub>3</sub>.

{|align="center"  border="1" width="700" cellpadding="5"
|rowspan="2" align="center"|'''The chemical formula of Na<sub>2</sub>CO<sub>3</sub>'''
|colspan="3" align="center"|'''consists of:'''
|-
!number of Na atoms
!number of C atoms
!number of O atoms
|-
! one formula unit
|align="center"|[[File:2Na.gif]]<br/>'''two''' Na atoms 
|align="center"|[[File:1C.gif]]<br/> '''one''' C atom 
|align="center"|[[File:3O.gif]]<br/>'''three''' O atoms 
|-
! 12 formula units 
|align="center"|[[File:24Na.gif]]<br/>'''2'''(12) = 24 Na atoms 
|align="center"|[[File:12C.gif]]<br/>'''1'''(12) = 12 C atoms 
|align="center"|[[File:36O.gif]]<br/>'''3'''(12) = 36 O atoms 
|-
! one dozen formula units 
|align="center"|'''two''' dozens (= 24) <br/> [[File:24Na.gif]]<br/>2(12) Na atoms 
|align="center"|'''one''' dozen (= 12) <br/> [[File:12C.gif]]<br/>1(12) C atoms 
|align="center"|'''three''' dozens (= 36)<br/> [[File:36O.gif]]<br/>3(12) O atoms 
|-
! 6.022 x 10<sup>23</sup> formula units
|align="center"|[[File:sodiumatom_lots.gif]]'''2'''(6.022 x 10<sup>23</sup>) = 12.044 x 10<sup>23</sup> Na atoms 
|align="center"|[[File:carbonatom_lots.gif]] '''1'''(6.022 x 10<sup>23</sup>) = 6.022 x 10<sup>23</sup> C atoms 
|align="center"|[[File:oxygenatom_lots.gif]] '''3'''(6.022 x 10<sup>23</sup>) = 18.066 x 10<sup>23</sup> O atoms 
|-
!one mole formula units 
|align="center"|'''2''' moles (= 12.044 x 10<sup>23</sup>) Na atoms 
|align="center"|'''1''' mole  (= 6.022 x 10<sup>23</sup>) C atoms 
|align="center"|'''3''' moles  (= 18.066 x 10<sup>23</sup>) O atoms 
|}

==Number ratio of the ions==
A chemical formula gives the number ratio of the ions present in the ionic compound. This means that the ratios are the same if you count in individual ions, dozens of ions, or moles of ions.   

Take a look at the ratio of the ions in sodium carbonate, Na<sub>2</sub>CO<sub>3</sub>. 
{|align="center"  border="1" width="700" cellpadding="5"
|rowspan="2" align="center"|'''The chemical formula of Na<sub>2</sub>CO<sub>3</sub>'''
|colspan="2" align="center"|'''consists of:'''
|-
!number of Na<sup>+</sup> ions
!number of CO<sub>3</sub><sup>2-</sup> ions
|-
! one formula unit
|align="center"|'''two''' Na<sup>+</sup> ions 
|align="center"|'''one''' CO<sub>3</sub><sup>2-</sup> ion
|-
! one dozen formula units
|align="center"|'''two''' dozens  Na<sup>+</sup> ions 
|align="center"|'''one'''  dozen CO<sub>3</sub><sup>2-</sup> ion
|-
! one mole formula units
|align="center"|'''two''' moles  Na<sup>+</sup> ions 
|align="center"|'''one'''  mole CO<sub>3</sub><sup>2-</sup> ion
|-
|}

==Content suitability==
BCIT courses:
<span class="pops">[http://www.bcit.ca/study/outlines/chem0011  CHEM 0011]</span>