In 1 mole of sodium carbonate (Na_2CO_3Na2CO3) there would be 2 moles of sodium ions (#Na^+).
Sodium ions have a +1 charge (Na^+Na+), and carbonate ions have a -2 charge (CO_3^-2CO−23) so you know that these ions must combine in a 2:1 ratio to give a compound which has no charge (electrically neutral).
Once you have determined the chemical formula, let's consider what it means.
Na_2CO_3Na2CO3 = is the chemical formula for sodium carbonate
Imagine you have just one unit sodium carbonate - you would have 2 ions of Na.
If you had 10 units of Na_2CO_3Na2CO3 you would have 20 sodium ions.
100 units of Na_2CO_3Na2CO3 would have 200 sodium ions.
1,000,000 units of Na_2CO_3Na2CO3 would have 2,000,000 sodium ions.
Now multiply by a really big number, 6.022 x 10^236.022x1023
You would have 1.2044 x 10^241.2044x1024 sodium ions, which is 2 moles.
The important thing is the ratio. Since the ratio is 2:1, 1 mole of Na_2CO_3Na2CO3 will have 2 moles of Na.
Hope this helps!
Noel P.
