How on earth do you do this? What percent by weight of Na2S2O3 is Sodium (Na)? (Na, 23; S, 32; 0, 16) Okay that looks confusing but. The "Na2S2O3" isn't suppose to be spelled like that. It's Na (then a 2 that is haflway beneath the number) And then you repeat with S (lower 2), O and lower 3. It's hard to explaina and i don't know what it's called. But how do i solve this?