Question

The valence electron in potassium requires `6.95 xx 10^-19` `"J"` of energy to be removed. What frequency of light can do this? What type of electromagnetic radiation could do this?

Answer 1

Very blue visible photons or UV photons.

Explanation:

`K` electron configuration: `[Ar]4s^1`

This electron in the `4s` orbital requires `E = 6.95*10^-19 J` to be emitted. This is merely a question of the photon's energy being that which meets this requirement, thus,

`6.95*10^-19 J = (6.626*10^-34 J*s)v`
`v = 1.05*10^15 s^-1`

Now, referring to the EMR diagram that I gaurantee you most people don't have absolutely memorized:

This energy corresponds with the frequency of very blue photons (visible) or UV photons.