Beryllium and magnesium do not give colo...

Beryllium and magnesium do not give colour to flame whereas other alkaline eath metals do so. Why?

Text Solution

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Because of the small size, the ionisation enthalpies of `Be` and `Mg` are much higher than those of other alkaline earth metals. Therefore, they need large amount of energy for excitation of electrons to higher energy levels. Since such a large amount of energy is not available in Bunsen flame, therefore, these metals do not impart any colour to the flame.

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Beryllium and magnesium do not impart any colour to the flame test. The reason is that

lower value of ionisation value

higher value of ionisation energy

larger size of alkali earth metal

Both (2) and (3) are correct

Beryllium has less negative value of reduction potentials compared to other alkaline earth metals due to:

the smaller hydration energy of the `Be^(2+)`

the large value of the atomization enthalpy of the `Be` metal.

the large value of ionisation of the `Be `metal.

`(b)` and `(c)` both

Assertion (A): Be and Mg impart characterstic colour to the flame. Reason (R ): As compared to other alkaline earth metals, ionisation enthalpy of Be and Mg is low.

If both `(A)` and `(R )` are correct and `(R )` is the correct explanation of `(A)`.

If both `(A)` and `(R )` are correct, but `(R )` is not the correct explanation of `(A)`.

If `(A)` is correct, but `(R )` is incorrect.

If `(A)` is incrrect, but `(R )` is correct.