Question

What color is the flame test for calcium?

Answer 1

Calcium ions give an orange-red color in a flame test. The ground state electron configuration for the calcium 2+ ion is `"1s"^2"2s"^2"2p"^6"3s"^2"3p"^6`. When the electrons are heated, they become excited (energized), and jump to any higher energy level available, such as 7s or 5p. The excited electrons are unstable, and they drop back down to the ground state. However, they may drop in two or more stages, such as from 7s to 6s to 3p. Each drop releases light energy of a specific wavelength. This is why the emission spectra for the elements are line spectra and not continuous. The flame test color is a combination of the different wavelengths of light emitted by the excited electrons when they drop down to lower energy levels.

The flame test for calcium is:

The emission line spectrum for calcium is:

Here is a video which shows flame tests of aqueous solutions of a number of metal chloride compounds. Calcium chloride is shown at starting at the 12s point of the video. Note the yellow-orange color produced!

Video from: Noel Pauller