Main Group (1A-4A)

Group 1A: Alkali Metals

Elements with ns¹ valence electron configuration

Exception: Hydrogen is the only non-metal

React vigorously with H₂O to produce H₂ (g)

• 2M(s) + 2H₂O(l) → 2M⁺(aq) + 2OH^-(aq) + H₂(g)

Na and K are essential for the proper function of nerves and muscles (sodium potassium pump)

Methods of Preparation of Pure Alkali Metals

Li: Electrolysis of molten LiCl

Na: Electrolysis of molten NaCl

K: Electrolysis of molten KCl

Rb: Reduction of RbOH with Mg and H₂

Cs: Reduction of CsOH with Mg and H₂

Selected Reactions of the Alkali Metals

2M + X₂ → 2MX (X₂ is any halogen)

4Li + O₂ → 2Li₂O (Excess Oxygen)

2Na + O₂ → Na₂O₂

M + O₂ → MO₂ (M = K, Rb, or Cs)

2M + 2H₂O → 2MOH + H₂

Types of oxides

Oxide ion = O^2- (Li₂O)

Peroxide ion = O₂^2- (Na₂O₂)

Superoxide ion = O₂^- (KO₂,RbO₂,CsO₂)

Chemistry of Hydrogen

Colorless and odorless gas

Non-polar

Highly flammable (18%-60% H₂ is considered flammable)

Diatomic

Sources of Hydrogen

1) Industrial sources: Reaction of methane with water at high temperatures and pressure in the presence of a metallic catalyst (nickel)

2) Electrolysis of water

3) By-product of gasoline production

Hydrogen Uses

Industrial Use: Production of ammonia by the Haber process

Hydrogenation of unsaturated vegetable oils

Hydrogen and Hydrides

Hydrogen behaves as a typical non-metal

• Forms covalent compounds with other nonmetals

• Salts with active mtals

Hydrides: Binary compounds containing hydrogen

Ionic (Salt-like) Hydrides

When hydrogen combines with the most active metals (Groups 1A and 2A)

Ex: LiH and CaH₂

Hydride ion acts as a strong reducing agent (strong base)

(LiH is a stronger base than LiOH)

Covalent Hydrides

Formed when hydrogen combines with other nonmetals

Ex: HCl, CH₄, and NH₃

Most important covalent hydride is water (H₂O)

Unusual Properties of Water (Due to its polarity)

High boiling point compared to its molar mass(100 degrees celsius)

Large Heat of Vaporization

Less dense as a solid

Excellent solvent for ionic and polar substances

Metallic (Interstitial Hydrides)

Formed when transition metal crystals are treated with H₂ gas

Small hydrogen atoms migrate into the crystal structure and occupy interstices (holes)

Lose much of the absorbed hydrogen as a gas when heated

• Offers possibilities for storing hydrogen for use as a portable fuel

• Ex: PdH_x, TiH_x

Group 2A: Alkaline Earth Metals

Valence Electron Configuration - ns²

Very reactive

Named after the basicity of their oxides (form basic oxides)

• Exception: Beryllium oxide (BeO) has some acidic properties (amphoteric)

Application of Alkaline Earth Metals

Calcium: Found in bones and teeth

Magnesium (Mg²⁺ ion):

• Essential in metabolism and muscle function

  • Useful structural material because of its low density and moderate strength

Method of Preparation of Alkaline Earth Metals

Electrolysis of their respective chloride (BeCl₂,MgCl₂,CaCl₂,SrCl₂,BaCl₂,RaCl₂)

Alkaline Earth Metal Reactions

M + X₂ → MX₂ (X₂ = any halogen)

2M + O₂ → 2MO (Ba gives BaO₂ as well)

M + 2H₂O → M(OH)₂ + H₂ (M = Ca, Sr, or Ba)

Alkaline Earth Metals and Ion Exchange

Hard water: Natural water that contains Ca²⁺ and Mg²⁺ ions. These ions interfere with detergents and forms precipitates with soap

• Ion exchange: the process that removes Ca²⁺ and Mg²⁺ (Water softener)

• Na⁺ ions are released into solution

• Ion-exchange resin: Where the Ca²⁺ and Mg² ions swap with Na⁺

• Mg and Ca are bad for your kidneys and hair

  • People with high blood pressure shouldn’t drink soft water (should drink bottled water)

Group 3A Elements (Icosagens)

Valence electron configuration: ns²np¹

Increase in metallic character going down the group

Boron

Technically a metalloid, but it generally acts as a nonmetal → forms covalent compounds

Boranes: Covalent hydride compounds of boron (Ex: B₂H₆)

Electron-deficient → very reactive

React exothermically with oxygen

• Once evaluated as fuels for rockets in the U.S. space program

Group 3A Methods of Preparation

B: Reduction by Mg or H₂

Al: Electrolysis of Al₂O₃ in molten Na₃AlF₆

Ga: Reduction with H₂ or electrolysis

In: Reduction with H₂ or electrolysis

Tl: Electrolysis

Aluminum

Most abundant metal on earth (oxygen is the most abundant nonmetal)

Metallic properties: Conducts heat and electricity, lustrous appearance

Forms covalent bonds with nonmetals

Gallium

Similar to aluminum

Low melting point and high boiling point → largest liquid range of any metal

Used in thermometers

Expands when it freezes

Indium and Thallium

Indium: Similar to Ga and Al

Thallium: Only pure metal in group 3A (chemistry is completely metallic)

Group 3A Reactions

2M + 3X₂ → 2MX₃ (X₂ = any halogen molecule; Tl gives TlX as well, but no Tll₃)

4M + 3O₂ → 2M₂O₃ (High temperatures; Tl gives Tl₂O as well)

Group 4A (Crystallogens)

Valence electron configuration: ns²np²

Carbon is necessary for life

Silicon forms the basis for the geological world

Group 4A Properties

Form four covalent bonds to nonmetals

Carbon forms pi bonds (double and triple bonds)

• Chemistry of carbon is dominated by carbon-carbon bonds

  • Chemistry of silicon is dominated by silicon-oxygen bonds

Group 4A Element Properties

Carbon: Occurs in the allotropic forms of graphite, diamond, and fullerenes

Silicon: Semimetal that is found widely distributed in silica and silicates

Germanium: Rare element and a semimetal

• Used in the manufacturing of semiconductors for transistors and similar electronic devices

Tin: Soft, silvery metal that can be rolled into thin sheets

• SnCl₂ is a famous reducing agent

Lead:

• Ore - Galena (PbS)

• Melts at low temperatures

• Toxic nature (Death of Ludwig Van Beethoven)