# Why flame color of salts is determined by metal

If a pure metal is heated up in a flame, we see it giving the flame a characteristic color, e.g. $\ce{Na}$ burns yellow.

If a salt, e.g. $\ce{NaCl}$ or $\ce{Na2SO4}$, is heated up, resulting color to a greater degree still is that of the pure metal. Although the color does change depending on the anion, this effect is usually not much pronounced.

Why is that the case? Shouldn't ionization happen to anions as well, causing electrons (including those pulled from the cation) to "fall back" and give off photons? In other words shouldn't we see a mix of two characteristic colors?

• Related: Anions produce flame color?. – airhuff May 28 '17 at 18:19
• I edited your post to make use of the \ce{...} notation to format the chemical formula correctly (upright with correct sub scripts). – NotEvans. May 28 '17 at 21:19