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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
Discuss the general characteristics and gradation in properties of alkaline earth metals.
Which one of the alkaline earth metal carbonates is thermally the most stable?
The product obtained as a result of a reaction of nitrogen with CaC2 is ______.
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.
Alkaline earth metal (A), belongs to 3rd period reacts with oxygen and nitrogen to form compound (B) and (C) respectively. It undergoes metal displacement reaction with AgNO3 solution to form compound (D). Identify A, B, C and D.
The reducing power of a metal depends on various factors. Suggest the factor which makes Li, the strongest reducing agent in aqueous solution.
When sodium is dissolved in liquid ammonia, a solution of deep blue colour is obtained. The colour of the solution is due to ______.
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.
Discuss the trend of the following:
The solubility and the nature of oxides of Group 2 elements.
Assertion (A): Beryllium carbonate is kept in the atmosphere of carbon dioxide.
Reason (R): Beryllium carbonate is unstable and decomposes to give beryllium oxide and carbon dioxide.
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.
PbCl4 exists but PbBr4 and Pbl4 do not because of ______.
