Li, Na, K, Rb, Cs are known as alkalimetals as their oxides on reaction with water to form hydroxides, which are strongly alkaline in nature. They have ns valency shell configuration and exhibit +1 oxidation state. They do not occur in free state due to high reactivity. They are soft, possess low density, melting point, boiling point, ionization potential, electron affinity, electronegativity. They have high electropositive character and metallic nature. Density of these elements increase from Li to Cs. Where as density of K is lessthan that of Na, due to abnormal increase in atomic size, vacant 3d sub-shell and inter atomic distance in the crystal lattice of potassium. They exhibit photo electric effect when they are exposed to light (due to emission of electrons). They give different colours with flame (due to excitation & de excitation of electrons). Li gives crimson red, Na gives golden yellow, K, Rb, Cs give violet colour. Alkali metals are also detected by photometry or atomic absorption spectroscopy.

The extent of hydration of these ions: Li⁺> Na⁺ > K⁺ > Rb⁺ > Cs⁺.
Electrical conductance of these ions in water: Li⁺< Na⁺< K⁺< Rb⁺< Cs⁺.
Due to high reactivity, Li is stored in paraffin, Na is stored in kerosene. On reaction with air Li forms monoxide, Na forms peroxide, others form super oxides. They give ionic hydrides with H₂.

Order of ionic nature of these hydrides: CsH > RbH > KH > NaH > LiH.
          Except Li, other elements give ionic halides with halogens. Sodium decomposes water to liberate H₂ gas. Due to small atomic size, high electronegativity, absence of d -orbitals Li exhibit anomalous properties like formation of carbides, Nitrides, hard metal, low solubilities of hydroxide, carbonate, phosphate and flouride. Li is diagonally related with Mg, due to similar atomic size, electronegativity, polarizing power. Li & Mg are slow to react with water, form nitrides, monoxides, their halides are covalent and chlorides are deliquescent, highly hydrated, carbonates, phosphates are sparingly soluble in & H₂O.
          Sodium is used as reagent in organic reactions (e.g.:Wurtz reaction), as a catalyst in the preparation of rubber, sodium amalgam, in lassaigne's test (to detect S, N, halogens). potassium is used as an electrolyte in storage batteries, in the manufacture of soft soaps, photo electric cells. Na, K help in maintaining osmotic pressure in the cell, essential for the synthesis of proteins, for the metabolism of glucose inside the cell, in producing electrical potential across the cell membrane, in Na ion transport from the cell (Sodium pump).
NaCl is used in diet, pickles, in preservation of meat, fish, to prepare freezing mixture with ice, in the manufacture of Na and Cl₂.
         Other important compound of Na is NaOH. It is known as caustic soda, as it decomposes the muscle proteins and makes pulp. It is used to absorb SO2 near electrical generators, in mercarizing cotton, refining of petroleum, soap, paper, rayon industries. NaOH can be manufactured by

1. Causticizing process (Gossage process): In this method milk of lime is added to 10% warm solution of Na₂ CO₃ to produce NaOH.
     Ca(OH)₂ + Na₂CO₃     CaCO₃ + 2 NaOH

 Castner - Kellner (Mercury cathode) process: This cell consists of a large rectangular iron tank. It's divided into three compartments by two slate partitions which are not touching the bottom of the tank, but goes into mercury. Mercury acts as an intermediate electrode due to induction.

Outer compartments are provided with graphite anodes, where Hg acts as cathode. This compartment is filled with brine solution. Reactions taking place in this compartment as follows.
2 NaCl → 2 Na⁺ + 2 Cl^-  
At anode:  2 Cl^-   → Cl₂ + 2 e^-  (Oxidation)
At cathode: 2 Na⁺ + 2 e^- + Hg → Na₂Hg (Reduction)
         Middle compartment is provided with a series of iron rods, acts as cathode, where Hg acts as anode. It is filled with dilute NaOH. Na₂Hg from outer compartment comes into middle compartment due to rocking motion of cell on eccentric wheel. Reactions taking place in the middle compartment are      
At anode : Na₂Hg → 2 Na +  2 e + Hg (oxidation)
At cathode : 2 H₂O + 2 e^-  → H₂ + 2 OH (Reduction)
                                  2 Na⁺ + 2 OH^-→ 2 NaOH

Properties of Na₂CO₃:
         It is white, crystalline, efflorescent solid. Its M.P.: 1125 K. It give alkaline solution due to anionic hydrolysis.
CO₃^-2 + 2 H₂O  →  H₂CO₃ + 2 OH^-
        Acids liberate CO₂ from Na₂CO₃, gives Na₂S₂O₃ with S and SO₂. Na₂S₂O₃ reacts with SiO₂ to give Na₂SiO₃.
Uses: Used to remove hardness of water, as a reagent in qualitative & quantitative analysis, refining petroleum, in glass, dye, paper industry, laundries, to prepare "ultra marines" [ultramarine is aluminosilicate and is used as pigment. 
    e.g.: Na₃(AlO₂)₆ (SiO₂)₆ Cl₂ - sodalite], to prepare fusion mixture (Na₂CO₃ + K₂CO₃ )

Sodium bi Carbonate: It is a white, crystalline solid. It does not give any colouration with phenolphthalein but gives pink colour with methyl orange indicator. It is used as antacid, in fire extinguishers, in baking cakes, effervescent drinks, reagent in laboratory.
Alkaline Earth Metals
         Mg, Ca, Ba, Sr, Ra (except Be) are known as alkaline earth metals as their oxides and hydroxides are alkaline in nature & their oxides are found in thin rockey outer layer of the earth's crust. General electronic configuration is ns², exhibit +2 oxidation state. Ca gives brick red, Ba gives apple green, Sr. gives Crimson red colour to the flame.
mportant minerals of Be are Beryl (3 BeO. Al₂O₃. 6 SiO₂), Phenacite (2 BeO. SiO₂), Ca are Dolomite (CaCO₃.MgCO₃), Gypsum (CaSO₄ . 2 H₂O), Sr are Celestite (SrSO₄), Strontianite (SrCO₃), Ba are Berytes (BaSO₄), Witherite (BaCO₃), Mg are Magnesite (MgCO₃), Carnallite (KCl. MgCl₂ .6 H₂O)

General Characteristics of Compounds of Alkaline Earth Metals: BeO, Be(OH)₂ are amphoteric in nature (reacts with acids and bases). Thermal stability, solubility increases from Mg(OH)₂ to Ba(OH)₂. Be halides are covalent, other halides are ionic. Carbonates of this group elements are insoluble in water. They decompose on heating. BeSO₄, MgSO₄ are soluble in water. The solubility decreases from CaSO₄ to BaSO₄. Nitrates decompose on heating Alkaline earth metal carbonates, sulphates solubility decreases down the group as the hydration enthalpies decrease down the group.
Anomalous behaviour of Be: Due to small atomic size, high electronegativity Be shows anomalous behaviour.
        Be compounds are covalent, not effected by dry air, amphoteric, do not respond to flame test, forms complexes, maximum covalency is 4 (for other elements is 6).

Diagonal relationship with Al: Both Be & Al forms covalent compounds, undergo hydrolysis, forms complexes and passive by conc. HNO₃ loss of initial reactivity of Be, Al, Fe, Cr with conc. HNO₃ is known as "passivity" Be & Al are amphoteric metals. Carbides on hydrolysis give methane, and they are called "Methanides".
II A elements react with H₂ to form ionic hydrides.
Order of ionic nature: BaH₂ > SrH₂ > CaH₂ > MgH₂ > BeH₂
        Be forms covalent, hygroscopic halides, which can fume in air on hydrolysis. Other elements form ionic halides. Be is used in making electrodes in neon signs, Cu alloys; Mg is reducing agent and deoxidiser in metallurgy, to prepare alloys like electron magnalium.
Compounds of Calcium: CaO is called as quick lime, Ca (OH)₂ is slaked lime, CaSO₄ . 2 H₂O is gypsum, CaSO₄ .  H₂O is plaster of paris. A mixture of 1 part of slaked lime, Water and 3 parts of sand is known as "mortar" sand makes the mass porous and prevents the formation of cracks.
         setting of mortar is due to the formation of CaSiO₃
         Ca(OH)₂ + SiO₂→ CaSiO₃ + H₂O
         When mortar is mixed with Cement, it is called "Cement mortar". Lime Stone and Clay on heating gives "Hydraulic Mortar". Which is an antiseptic and bleaching agent. Gypsum on heating upto 393 K gives plaster of paris, above 393 K gives "dead burnt plaster".

Role of Mg⁺²: Chlorophyll in plants contain Mg⁺². It is cofactor for the enzymes that utilise ATP in Phosphate transfer. Enzymes "Phosphohydrolase" & "Phosphotransferases" contain
Mg⁺². It is present in animal cells.
 

CEMENT
Cement is an important building material, introduced by Joseph Aspdin. The average composition of cement is
CaO : 50 - 60%
SiO₂ : 20 - 25%
Al₂O₃ : 5 - 10%
MgO : 2 - 3%
Fe₂O₃ : 1 - 2%
SO₃ : 1- 2%
For good quality of cement, the ratio of SiO₂ to Al₂O₃ must be between 2.5 - 4.0. Cement is basically a mixture of clinker (formed by clay and lime on strong heating) and 2-3% Gypsum (to regulate the setting time). Cement is used in concrete and plastering. It is used in the construction of dams, bridges, roads, tunnels etc.