Question

At the occasion of marriage, the fireworks contain:
A.$Ba$
B.$K$
C.$Be$
D.$Na$

Answer 1

The colour of flames could be observed due to the presence of empty orbitals in the transition metals.
-The electrons from ground state get excited to a higher state when exposed to high temperature, and while coming back to the ground state it releases energy in the form of radiation which falls in the visible region of the spectrum.

Complete step by step answer:
We will use the knowledge of flame test to answer this question because flame test is applicable only in case of metal ions and all the options given in the question are metals.
A flame test is an analytical process which is used in the field of chemistry in order to detect the presence of some specific elements, primarily metal ions, based on the characteristic of each element's emission spectrum. The colour of flames in general also is dependent on the temperature in which the experiment is carried out.
We know that apart from barium, none of the metals given in the options are transition metal. So they will not have empty orbitals, for the process.
The presence of empty orbitals in the transition elements makes it possible for us to see the colour of flame. This is because when the electrons from the ground state are exposed to higher temperature, as in when they are heated, they are excited to a higher excited state. When the temperature comes down, and the electrons start to come back to their original ground state, we can observe that it releases energy in the form of radiation. And we know that radiations can be categorised into different types, on the basis of their wavelength and frequency, for instance visible region, ultraviolet region, infrared region etc. So it is observed that, these radiations which are created by the electrons, fall in the visible region of the spectrum. This is the reason, the colour of the light is visible to us, as in the flame of the fireworks impart colour.
In the given question, since barium imparts apple green colour to the flame, it is being used in the fireworks.
So the correct answer is, option A.

Note: Other elements which impart colour to the flame are, arsenic which gives blue colour, boron gives bright green, beryllium white, and calcium brick red etc.
-In the labs, we usually make a paste of the compound under consideration, with conc. Hydrochloric acid and then with the help of a glass rod, we do the flame test.