Advertisements
Advertisements
Question
What are the common physical features of alkali metals?
Advertisements
Solution
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.
RELATED QUESTIONS
What are the common chemical features of alkali metals?
Why are potassium and cesium, rather than lithium used in photoelectric cells?
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
Write a balanced equation for the reaction between KO2 and water.
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 ______.
Metals form basic hydroxides. Which of the following metal hydroxide is the least basic?
The solubility of metal halides depends on their nature, lattice enthalpy and hydration enthalpy of the individual ions. Amongst fluorides of alkali metals, the lowest solubility of LiF in water is due to ______.
By adding gypsum to cement
When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li, Na and K.
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.
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 metal mainly used in devising photoelectric cells 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 ______.
KO2 (potassium super oxide) is used in oxygen cylinders in space and submarines because it ______.
