Question

Why do some metals glow when burning in a flame?

Answer 1

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 #"Na"#, #"Ca"#, #"Sr"#, #"Ba"#, #"Cu"# give out radiation with frequencies inside the visual spectrum. so we are able to see them.

But metals such as #"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 #"Mg"# is faced with a burning flame.