How do you draw the Lewis structure of compound with an ionic bond

[Na]^+ [Cl]^-

Explanation:

Lets say its sodium, its number of electrons is 11, but when its stable (an ion), it is 10. and chloride, number of electrons is 17, but when its stable (an ion) it is 18. So the lewis structure for that is, remember with the straight brackets (not sure what it's called, but you know what I mean I guess) its this one: [ ]

Sodium will be + because it has more protons (11-10 = +1), and chloride will be - because it gained an electron, so has more electrons than protons (17-18 = -1)

So the lewis structure would be:

[Na]^+  for sodium

and

[Cl]^- for chlorine

Sodium chloride:

[Na]^+ [Cl]^-

Also just to add, only 1 of each atom (Na and Cl) was needed for the bonding, but if let's say example; 2 Cl was needed to bond with sodium, there would be 2 Cl (same) and 1 Na.

1st you need to find the mole ratio between KClO3 and O2.  To find that you need to take the coefficents of each of the compounds.  That gives a ratio of 2:3.

Now we find out how many each unit is:
2x = 12
x = 6

Now we multiply it by 3 to find the number of moles of O2
3(6) = 18 mol O2.