The alkali metals have one valence electron and are the most electropositive metals. They have large atomic and ionic radii that increase down the group, and their hydration enthalpies decrease with increasing size. Alkali metals are soft, silvery-white metals with low melting and boiling points that are highly reactive due to their large size and low ionization enthalpy, with reactivity increasing down the group. They react with air, water, dihydrogen, and halogens. Uses include lithium in batteries, aluminum in aircraft, and potassium chloride as fertilizer.

2. ELECTRONIC CONFIGURATION
ALL THE ALKALI METALS HAVE ONE VALENCE
ELECTRON, ns1
eg:Li-1s2 2s1
Na-1s2 2s2 2p6 3s1
THE MOST ELECTROPOSITIVE METALS.

3. ATOMIC AND IONIC RADII
• Alkali metal atoms have largest sizes
• The atomic and ionic radii of alkali metals
increase on moving down the group

4. HYDRATION ENTHALPY
• The hydration enthalpies of alkali metal
ions decrease with increase in ionic sizes
Li+>Na+>K+>Rb+>Cs+

5. PHYSICAL PROPERTIES
• Alkali metals are silvery white, soft and light
metals
• Low density
• Low melting point and boiling points

6. CHEMICAL PROPERTIES
• Alkali metals are highly reactive due to their
large size
• Low ionization enthalpy
• The reactivity of metals increases down the
group

7. REACTIVITY TOWARDS AIR
• Alkali metals in dry air due to the formation
of their oxide
• Lithium forms monoxide
4Li+o2 2Li2o

8. REACTIVITY TOWARDS WATER
• The alkali metals react with water to
form hydroxide and dihydrogen
2M+2H2O 2M++2OH-+H2
(M=an alkali metal)

9. REACTIVITY TOWARDS DIHYDROGEN
• Alkali metals react with dihydrogen to
form hydrides
2M+H2 2M+H-

10. REACTIVITY TOWARDS HALOGENS
• Alkali metals react with halogens to
form ionic halide

11. USES
• Lithium metal bearing for motor
engines.
• Aluminium to make aircraft parts.
• Lithium also used to make
electrochemical cells.
• Potassium chloride is used as fertilizer.