In 1 mole of sodium carbonate (#Na_2CO_3#) there would be 2 moles of sodium ions (#Na^+).

Sodium ions have a +1 charge (#Na^+#), and carbonate ions have a -2 charge (#CO_3^-2#) 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_3# = 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_3# you would have 20 sodium ions.

100 units of #Na_2CO_3# would have 200 sodium ions.

1,000,000 units of #Na_2CO_3# would have 2,000,000 sodium ions.

Now multiply by a really big number, #6.022 x 10^23#

You would have #1.2044 x 10^24# sodium ions, which is 2 moles.

The important thing is the ratio. Since the ratio is 2:1, 1 mole of #Na_2CO_3# will have 2 moles of Na.

Hope this helps!

Noel P.