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प्रश्न
Why are alkali metals not found in nature?
उत्तर
Alkali metals include lithium, sodium, potassium, rubidium, cesium, and francium. These metals have only one electron in their valence shell, which they lose easily, owing to their low ionization energies. Therefore, alkali metals are highly reactive and are not found in nature in their elemental state.
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संबंधित प्रश्न
Explain why alkali and alkaline earth metals cannot be obtained by chemical reduction methods?
Why are potassium and cesium, rather than lithium used in photoelectric cells?
When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
Write a balanced equation for the reaction between KO2 and water.
Which of the alkali metal is having least melting point?
Which one of the following alkali metals gives hydrated salts?
The alkali metals are low melting. Which of the following alkali metal is expected to melt if the room temperature rises to 30°C?
Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?
The order of decreasing ionisation enthalpy in alkali metals is ______.
In the synthesis of sodium carbonate, the recovery of ammonia is done by treating NH4Cl with Ca(OH)2. The by-product obtained in this process is ______.
By adding gypsum to cement
Metallic elements are described by their standard electrode potential, fusion enthalpy, atomic size, etc. The alkali metals are characterised by which of the following properties?
(i) High boiling point.
(ii) High negative standard electrode potential.
(iii) High density.
(iv) Large atomic size.
Which of the following compounds are readily soluble in water?
(i) BeSO4
(ii) MgSO4
(iii) BaSO4
(iv) SrSO4
When a metal of group 1 was dissolved in liquid ammonia, the following observations were obtained:
(i) Blue solution was obtained initially.
(ii) On concentrating the solution, blue colour changed to bronze colour.
How do you account for the blue colour of the solution? Give the name of the product formed on keeping the solution for some time.
Ions of an element of group 1 participate in the transmission of nerve signals and transport of sugars and aminoacids into cells. This element imparts yellow colour to the flame in flame test and forms an oxide and a peroxide with oxygen. Identify the element and write chemical reaction to show the formation of its peroxide. Why does the element impart colour to the flame?
Match List-I with List-II.
| List-I | List-II |
| (Metal) | (Emitted light wavelength (nm)) |
| (a) Li | (I) 780.0 |
| (b) Na | (II) 455.5 |
| (c) Rb | (III) 670.8 |
| (d) Cs | (IV) 589.2 |
Choose the most appropriate answer from the options given below:
The correct order of conductivity of ions in water is ______.
KO2 (potassium super oxide) is used in oxygen cylinders in space and submarines because it ______.
