Alkali and alkaline earth metals, found in Groups 1 and 2 of the periodic table, are highly reactive elements. Their low ionization energies and electron configurations make them eager to form ionic compounds, shaping their unique properties and applications.

These metals react vigorously with water, producing hydrogen gas and metal hydroxides. Their oxides, hydroxides, and salts play crucial roles in various industries, from soap making to water treatment. Understanding their behavior is key to grasping s-block chemistry.

Properties and Trends

Characteristics of Alkali and Alkaline Earth Metals

• Alkali metals occupy Group 1 of the periodic table include lithium, sodium, potassium, rubidium, cesium, and francium
• Alkaline earth metals found in Group 2 consist of beryllium, magnesium, calcium, strontium, barium, and radium
• Both groups exhibit high reactivity due to their low ionization energies and electron configurations
• Alkali metals form +1 ions while alkaline earth metals form +2 ions when reacting
• Soft, silvery-white metals with low melting and boiling points (sodium melts at 97.8°C)
• Excellent conductors of heat and electricity due to their metallic bonding

Reactivity and Periodic Trends

• Reactivity increases down the group for both alkali and alkaline earth metals
• Larger atomic size and lower ionization energy contribute to increased reactivity
• Alkali metals react vigorously with water producing hydrogen gas and metal hydroxides
• Alkaline earth metals also react with water but less vigorously than alkali metals
• Flame tests used to identify specific metals based on characteristic colors emitted (sodium produces yellow flame)
• Electronegativity decreases down the group, affecting compound formation and properties

Diagonal Relationships and Analytical Techniques

• Diagonal relationship exists between certain elements in adjacent groups (lithium and magnesium)
• Similar physical and chemical properties observed in diagonally related elements due to comparable charge density
• Flame tests serve as qualitative analytical technique for metal identification
• Atomic absorption spectroscopy provides quantitative analysis of metal concentrations
• X-ray fluorescence spectroscopy used for non-destructive elemental analysis of samples

Oxides and Hydroxides

Formation and Properties of Hydroxides

• Alkali metal hydroxides highly soluble in water form strong bases (sodium hydroxide, potassium hydroxide)
• Alkaline earth metal hydroxides less soluble but still form basic solutions
• Hydroxides react with acids in neutralization reactions producing salts and water
• Industrial applications of hydroxides include soap production, paper manufacturing, and water treatment
• Preparation of hydroxides often involves electrolysis of aqueous salt solutions

Oxides and Their Reactivity

• Alkali metal oxides form when metals react with limited oxygen supply
• Alkaline earth metal oxides produced by direct combination of elements or thermal decomposition of carbonates
• Both groups of oxides react with water to form corresponding hydroxides
• Amphoteric nature observed in some alkaline earth oxides (beryllium oxide)
• Applications of metal oxides in ceramics, glass production, and catalysis

Peroxides and Superoxides

• Peroxides contain the peroxide ion (O₂²⁻) formed by alkali and some alkaline earth metals
• Superoxides contain the superoxide ion (O₂⁻) formed only by alkali metals except lithium
• Hydrogen peroxide (H₂O₂) decomposes to water and oxygen, used as bleaching agent and disinfectant
• Sodium peroxide (Na₂O₂) used in oxygen candles for emergency oxygen supply
• Potassium superoxide (KO₂) employed in air purification systems, releasing oxygen when reacting with carbon dioxide

Salts and Hydrides

Halides and Their Applications

• Alkali and alkaline earth metal halides form ionic compounds with halogens
• Sodium chloride (table salt) essential for biological processes and food preservation
• Calcium chloride used as de-icing agent and drying agent in organic synthesis
• Lithium bromide employed in absorption refrigeration systems
• Potassium iodide added to table salt as dietary supplement to prevent iodine deficiency

Hydrides and Their Reactivity

• Metal hydrides contain the hydride ion (H⁻) bonded to the metal
• Ionic hydrides formed by alkali and alkaline earth metals except beryllium and magnesium
• Sodium hydride (NaH) used as a strong base in organic synthesis
• Calcium hydride (CaH₂) serves as a drying agent for organic solvents
• Metal hydrides react vigorously with water producing hydrogen gas and metal hydroxides

Carbonates, Nitrates, and Sulfates

• Metal carbonates form by reaction of metal oxides with carbon dioxide
• Thermal decomposition of carbonates produces metal oxides and carbon dioxide
• Sodium carbonate (washing soda) used in glass production and water softening
• Nitrates highly soluble in water, used in fertilizers and explosives
• Calcium sulfate (gypsum) employed in construction materials and medical casts
• Barium sulfate used as contrast agent in X-ray imaging due to its insolubility