rank the group 1a elements tested in order of increasing energy emission when electrons returns to the ground state. explain this pattern in terms of changes in energy levels.

The increasing order of energy emission is as follow Li < Na < K < Rb < Cs

Explanation:

The Characteristic colors of alkali metals are Li-crimson red Na - golden yellow K - pale violet Rb and Cs - violet These flame color show that when we moved from down the group, the wavelength decreases (frequency increases). As the color of Li is red that shows, it has less emission energy as compare to Rb and Cs that have color violet (more emission energy).