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प्रश्न
Beryllium and magnesium do not give colour to flame whereas other alkaline earth metals do so. Why?
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उत्तर
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.
संबंधित प्रश्न
Which one of the alkaline earth metal carbonates is thermally the most stable?
Assertion: Generally alkali and alkaline earth metals form superoxides.
Reason: There is a single bond between O and O in superoxides.
Assertion: BeSO4 is soluble in water while BaSO4 is not
Reason: Hydration energy decreases down the group from Be to Ba and lattice energy remains almost constant.
In context with beryllium, which one of the following statements is incorrect?
Discuss briefly the similarities between beryllium and aluminium.
Beryllium halides are covalent whereas magnesium halides are ionic why?
Explain the important common features of Group 2 elements.
Why alkaline earth metals are harder than alkali metals?
The reducing power of a metal depends on various factors. Suggest the factor which makes Li, the strongest reducing agent in aqueous solution.
Some of the Group 2 metal halides are covalent and soluble in organic solvents. Among the following metal halides, the one which is soluble in ethanol is ______.
Identify the correct formula of halides of alkaline earth metals from the following.
(i) BaCl2.2H2O
(ii) BaCl2.4H2O
(iii) CaCl2.6H2O
(iv) SrCl2.4H2O
Name an element from Group 2 which forms an amphoteric oxide and a water soluble sulphate.
Discuss the trend of the following:
Thermal stability of carbonates of Group 2 elements.
What is the structure of BeCl2 molecule in gaseous and solid state?
An element of group 2 forms covalent oxide which is amphoteric in nature and dissolves in water to give an amphoteric hydroxide. Identify the element and write chemical reactions of the hydroxide of the element with an alkali and an acid.
Alkaline earth metals show ______.
Among the following alkaline earth metal halides, one which is covalent and soluble in organic solvents is ______.
Given below are two statements:
Statement I: Colourless cupric metaborate is reduced to cuprous metaborate in a luminous flame.
Statement II: Cuprous metaborate is obtained by heating boric anhydride and copper sulphate in a non-luminous flame.
In the light of the above statements, choose the most appropriate answer from the options given below.
