Question

A firework gave bright crimson light. It probably contained a salt of ____________ .
(A) Ca
(B) Sr
(C) Ba
(D) Mg

Answer 1

Some metals upon formation of ions tend to bring color to the flame when brought in contact with it. The metal ions have characteristic color due to electron transitions in the vacant orbitals. When the electron starts to come to the lower orbital after excitation, it will release energy in the form of light. Identify the metal ion that goes through the above process and gives crimson red colour.

Complete step by step answer:
Electron excitation is the transfer of a bound electron to a more energetic or rather higher energy orbital. However, the electron still remains bound to the atom.
There are many ways of exciting an electron like,
- Photoexcitation
- Electrical excitation
- Thermal excitation
Once the electron uses up all the energy, it starts to get back to its ground state. In this process, it releases the energy which was originally supplied to it. This is seen as coloration to the flame.
When strontium ion is brought to the flame, the electron present in 3d subshell releases energy in the way explained above. Strontium provides a characteristic bright crimson red color to the flame.
So, the correct answer is “Option B”.

Note: It is important to know that all transition metals produce a characteristic color to the flame. This is because they have unpaired electrons in the 3d subshell. These electrons get excited and during de excitation release energy in the form of light.