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प्रश्न
What are the common physical features of alkali metals?
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उत्तर
Physical properties of alkali metals are as follows.
- They are quite soft and can be cut easily. Sodium metal can be easily cut using a knife.
- They are light coloured and are mostly silvery-white in appearance.
- They have low density because of their large atomic sizes. The density increases down the group from Li to Cs. The only exception to this is K, which has a lower density than Na.
- The metallic bonding present in alkali metals is quite weak. Therefore, they have low melting and boiling points.
- Alkali metals and their salts impart a characteristic colour to flames. This is because the heat from the flame excites the electron present in the outermost orbital to a high energy level. When this excited electron reverts back to the ground state, it emits excess energy as radiation that falls in the visible region.
- They also display a photoelectric effects. When metals such as Cs and K are irradiated with light, they lose electrons.
संबंधित प्रश्न
Why are alkali metals not found in nature?
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?
Write a balanced equation for the reaction between KO2 and water.
Write a balanced equation for the reaction between Na2O and CO2.
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?
Which of the following elements does not form hydride by direct heating with dihydrogen?
When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li, Na and K.
The ease of absorption of the hydrated alkali metals ions in an ion-exchange resin follows the order:
Match List-I with List-II.
| List-I | List-II |
| (Metal) | (Application) |
| (a) Cs | (I) High temperature thermometer |
| (b) Ga | (II) Water repellent sprays |
| (c) B | (III) Photoelectric cells |
| (d) Si | (IV) Bullet proof vest |
Choose the most appropriate answer from the options given below:
A white precipitate was formed when BaCl2 was added to extract of an inorganic salt. Farther, a gas 'X' with characteristic odour was released when the formed white precipitate was dissolved in dilute HCl. The anion present in the inorganic salt is ______.
The correct order of hydration enthapies of alkali metal ions is ______.
Nitrogen combines with metals to form ______.
The correct order of conductivity of ions in water is ______.
Alkali metals are powerful reducing agents because ______.
Which element from following is used as moderator in nuclear reactor?
