Question

Which is the characteristic flame coloration of $Li$?
A. Yellow
B. Blue
C. Violet
D. Crimson red

Answer 1

Metal changes the color of a flame when they are heated in it. Different metals give different colors to the flame. So flame tests can be used to identify the presence of a particular metal in a sample. Alkali metals impart properties of colors to the flame due to low ionization enthalpy.

Complete answer:
The alkali metals and their salts impart a property of color to flame. On heating an alkali metal or its salt (particularly chlorides because of its more unstable nature in a flame), the electrons are energized effectively to higher energy levels in view of assimilation of energy. At the point when these electrons return to their ground states, they discharge additional energy in type of radiations which fall in the visible region thereby imparting a characteristic color to the flame. Lithium salts display red color at frequency $680.7\,nm$.
The alkali metals and their salts give characteristic color to Bunsen flame. The flame energy causes an excitation of the outermost electron which on reverting back to its initial position gives out the absorbed energy as visible light. The energy released at a minimum in the case of $Li$ and increases the order.

Note:
Lithium flame test. Positive result of a flame test for lithium, producing a red color. This is due to the excitation of electrons in the lithium by the heat of the flame. As these electrons lose their energy, they emit photons of red light. The color of the flame is different for different elements and can be used to identify unknown substances. The metal compound being tested here is lithium bromide.