↪ Alkali metals belong to ⅠA group.
↪ They have single electron in the outer most shell which occupy in s-orbital.
↪ Therefore, alkali metals are also known as s- block elements .
↪ These elements are called alkali since they react with water to give alkali.
General characters of alkali metals
⁕ Physical Properties
1. Physical state
↪ All the alkali metals are very soft, silvery white and can easily be cut.
2. Atomic and ionic sizes
↪ They have largest atomic and ionic radii in their corresponding period.
↪ They are all monovalent and strong electropositive in nature.
4. Oxidation state
↪ All alkali metals exhibit +1 oxidation state in combine state.
5. Ionization Energy
↪ They have lowest I.E. of all other elements in their respective period.
↪ They are excellent good conductor of heat and electricity.
↪ They are lower electronegative elements due to their large atomic size.
8. Melting and Boiling point
↪ They have very low melting and boiling point.
9. Reducing agent
↪ They have higher tendency to lose electron. That is why they are powerful reducing agent.
10. Flame color
↪ They produce characteristic color in the Bunsen burner. This property is helpful for identification of alkali metals by flame test. Color is produced due to electronic transition.
↪ The loosely held valence electron gains energy from flame and jumps to the higher energy level and after some time, it falls back to the lower energy level by emitting energy in the form of radiation in the visible region.
↪ So, different characteristic color is appeared. For example, lithium gives crimson color, sodium gives golden yellow color, potassium gives purple color etc.
↪ They are paramagnetic since they have unpaired electron in s- orbital of last shell.
⁕ Chemical Properties
1. Action with air
↪ Alkali metals are highly reactive in air and form their oxides. The reactivity increases down the group.
↪ It absorbs moisture to give sodium hydroxide which further absorbs CO2 from air and gets tarnished.
2. Action with water
↪ Alkali metals react with water vigorously (Li reacts slowly) to give hydrogen and alkali.
3. Reducing property
↪ All alkali metals are good reducing agent as they have lower I.E.
4. Action with halogens
↪ Alkali metals react with halogen to give their halides.
5. Action with liquid ammonia
↪ Alkali metals dissolve in liquid ammonia to form ammoniated metal ion and ammoniated electron.
↪ For long standing, the solution gives metal amide and hydrogen gas.
6. Action with acids
↪ All alkali metals react violently with acids to liberate hydrogen gas.
7. Action with hydrogen
↪ All alkali metals react with hydrogen at elevated temperature to form metallic hydride.