Why do some metals glow when burning in a flame?

Oct 25, 2015

The radiation that some metals emit falls inside the visual spectrum so we are able to see colours.

Explanation:

When faced with a burning flame, the electrons take energy to go to higher energy levels and emit radiation on their way back to lower energy levels.

Metals such as $\text{Na}$, $\text{Ca}$, $\text{Sr}$, $\text{Ba}$, $\text{Cu}$ give out radiation with frequencies inside the visual spectrum. so we are able to see them.

But metals such as $\text{Mg}$ emit radiation in the UV area and since human eye is not sensitive to UV radiation, we don't see any colour when a salt of $\text{Mg}$ is faced with a burning flame.

Watch this video of the flame test - credits to this video's owner