Question

Why do beryllium and magnesium not impact colour to the flame in the flame test?

Answer 1

When an alkaline earth metal is heated, the valence electrons get excited to a higher energy level. When this excited electron comes back to its lower energy level, it radiates energy, which belongs to the visible region. Hence, the colour is observed. In Be and Mg, the electrons are strongly bound. The energy required to excite these electrons is very high. Therefore, when the electron reverts back to its original position, the energy released does not fall in the visible region. Hence, no colour in the flame is seen.

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Answer 2

Hi,

Here is your answer,

As we know that all alkaline metals (except Be and Mg) impact a characteristic colour to the Bunsen flame. The different colours arises die to different energies required for electronic excitation and de-excitation.

Be and Mg atoms due to their small size, bind their electrons more strongly (because of higher effective nuclear charge). Hence, require high excitation energy and are not excited by the energy of the flame with the result that no flame colour is shown by them.


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