Alkali, Alkaline Earth, Earthy & Carbonoide Elements
Alkali Metals
The alkali metals, Lithium, Sodium, Potassium, Rubidium, Cesium, and Francium, are in Group 1 of the periodic table. They are named for the alkalinity of their compounds. Due to their chemical activity, they are not found in a free state and comprise almost 5% of the Earth’s crust (especially Sodium and Potassium).
Properties
- Electronic configuration: ns1
- Low first ionization energy
- Low electronegativity, decreasing down the group
- Common oxidation state: +1
- Form ionic compounds
- Low melting and boiling points
- Low density due to high volume and low atomic mass
- Strong reducing character with negative standard reduction potential
- Body-centered cubic structure
- Most salts (except Lithium) are water-soluble
Reactions
Alkali metals are highly reactive due to their strong reducing character, seeking a +1 oxidation state.
- With water (violent): 2 M(s) + 2 H2O → 2 MOH(aq) + H2(g)
- With hydrogen (high temperature): 2 M + H2 → 2 MH
- With halogens, sulfur: 2 M + X2 → 2 MX, 2 M + S → M2S
- With oxygen (except Lithium): 2 M + O2 → M2O2, 4 Li + O2 → 2 Li2O
- Lithium with nitrogen: 6 Li + N2 → 2 Li3N
Production Methods
Alkali metals are obtained by reducing their ionic compounds (oxidation state +1) through electrolysis or reactions with other alkali metals.
- Electrolysis of molten Sodium Chloride: 2 NaCl(l) → 2 Na(l) + Cl2(g)
- Electrolysis of molten Potassium Hydroxide: 2 KOH(l) → 2 K(l) + H2(g) + O2(g)
- Reaction with Sodium vapor: RbCl(l) + Na(g) → Rb(g) + NaCl(l)
Alkaline Earth Metals
These are the metallic elements in Group 2: Beryllium, Magnesium, Calcium, Strontium, Barium, and Radium. Beryllium and Magnesium have slightly different properties. They are named for their position between alkali metals and earthy elements, with many compounds being basic. They comprise over 4% of the Earth’s crust (especially Calcium and Magnesium).
Properties
- Electronic configuration: ns2
- Low ionization energy (higher than alkali metals), decreasing down the group
- Positive electron affinity
- Low electronegativity, decreasing down the group
- Common oxidation state: +2
- Mostly ionic compounds (except Beryllium)
- Lower water solubility compared to alkali metals
- Colors range from gray to white
- Harder than alkali metals, with variable hardness
- Reactive, but less than alkali metals, reactivity increases down the group
- Easily oxidized, good reducing agents
- Basic oxides and hydroxides (except Beryllium, which is amphoteric)
Reactions
- With water: M(s) + 2 H2O → M(OH)2(s) + H2(g)
- With non-metals: Form ionic compounds (except Beryllium and Magnesium)
- Reduces hydrogen: M(s) + 2 H+(aq) → M2+(aq) + H2(g) (Beryllium and Magnesium do not react with nitric acid)
Production Methods
- Electrolysis of molten halides: MX2(l) → M(l) + X2(g)
- Reduction of oxides with carbon: MO(s) + C(s) → M(s) + CO(g)
Applications
- Beryllium: Nuclear technology, alloys (low density, high strength, corrosion resistance)
Earthy Elements
Group 13 elements: Boron, Aluminum, Gallium, Indium, and Thallium. Named for their presence in earth (Aluminum is most abundant, 7% of crust). They are reactive, often found as oxides and hydroxides.
Properties
- Electronic configuration: ns2np1
- Boron is a non-metal/semiconductor (covalent bonds), others are metals (metallic character increases down the group)
- Boron is hard, metals are softer (Thallium can be scratched with a fingernail)
- Electronegativity is intermediate and irregular (except Boron)
- Common oxidation state: +3 (Ga, In, Tl also have +1)
- Boron oxides/hydroxides are acidic, Aluminum/Gallium are amphoteric, Indium/Thallium are basic
- Melting points are fairly low (except Boron), Gallium is liquid at 30°C
- Most salts are water-soluble
- Good reducing agents (especially Aluminum)
- Boron, Aluminum, Indium are good conductors, Gallium and Thallium are poor conductors
Reactions
- With water: Aluminum reacts, forming an oxide layer (2 Al(s) + 3 H2O → Al2O3(s) + 3 H2(g))
- With nitrogen: Boron and Aluminum form nitrides (2 B(s) + N2(g) → 2 BN(s))
- With halogens: 2 E + 3 X2 → 2 EX3
Production Methods
- Boron: Reduction of B2O3 with Magnesium
- Aluminum: Electrolysis of bauxite (AlO3(OH))
- Other metals: Electrolysis of aqueous salt solutions
Applications
Boron: Nuclear industry, semiconductor doping, alloys. Aluminum: Light, corrosion-resistant alloys. Gallium/Gallium Arsenide: Semiconductors. Indium: Alloys, semiconductors, photocells. Thallium: Glass.
Carbonoide Elements
Group 14 elements: Carbon, Silicon, Germanium, Tin, and Lead. Silicon is the second most abundant element in the Earth’s crust (after Oxygen). Carbon is a major component of organic matter. They are found in their natural state (Carbon, Tin, Lead) or as oxides and sulfides.
Properties
- Electronic configuration: ns2np2
- Carbon is a non-metal, Silicon/Germanium are semimetals, Tin/Lead are metals
- Carbon (diamond) is very hard, metals are soft (Lead can be scratched with a fingernail), semimetals have intermediate hardness
- Carbon has high melting/boiling points, decreasing down the group
- Oxidation states: +2, +4 (Carbon also has -4 in carbides, various in organic compounds)
- Carbon/Silicon oxides are acidic, Tin/Lead oxides are amphoteric
- Lead is toxic
Reactions
- Do not react with water
- Germanium, Tin, Lead react with acids
- Strong bases attack all except Carbon, releasing hydrogen
- React with oxygen to form oxides
Production Methods
- Silicon: Reduction of SiO2 with CaC2 in a coal furnace
- Germanium: Similar to Silicon or reduction of oxide with hydrogen
Applications
- Silicon/Germanium: Semiconductors (transistors)
- Silicon oxide: Glass manufacturing
- Carbon: Fuels, organic synthesis
- Tin: Welding, alloys
- Lead: Historically used in plumbing (being replaced due to toxicity)