CHM2046 Main-Group Chemistry & Periodic Trends

Vocabulary flashcards summarizing periodic trends, main-group reactivity, amphoteric behavior, industrial processes, and key reactions for CHM2046 final exam.

Ionization Energy

Energy needed to remove an electron from a gaseous atom; rises left-to-right across a period.

Electron Affinity

Energy released when an atom gains an electron; becomes more negative across a period.

Electronegativity

Ability of an atom to attract shared electrons; increases across a period.

Atomic Size Trend

Atomic radius shrinks across a period and grows down a group.

Metallic Character Trend

Metallic behavior decreases across a period, increases down a group.

Covalent Oxide

Oxide of a non-metal that forms an acid in water (acidic oxide).

Ionic Oxide

Metal oxide that forms a base in water (basic oxide).

Amphoteric Oxide

Oxide that reacts with both acids and bases; e.g., Al2O3, BeO.

Hydration Energy

Energy released when an ion is solvated; larger for small, highly charged ions.

Group 1A Reactivity

Alkali metals react vigorously with water; reactivity peaks at Cs.

Downs Cell

Electrolytic cell that produces liquid Na and Cl2(g) from molten NaCl.

Sodium Peroxide (Na2O2)

Product of 2 Na(s) + O2(g); a peroxide formed by sodium.

Potassium Superoxide (KO2)

Product of K(s) + O2(g); large K+ stabilizes O2⁻; used in rebreathers.

Reducing Power Order (K > Na > Li)

Among the lighter alkali metals, potassium is the strongest reducing agent.

Lithium Nitride (Li3N)

Compound formed when lithium reacts with N2; shows Li’s unique chemistry.

Group 2A Reactivity

Alkaline-earth metals; Mg reacts with steam, Ca with cold water; Ca more reactive.

Lattice Energy

Energy holding ions in a crystal; high values make many Group 2A salts poorly soluble.

Amphoteric Beryllium

Be compounds are covalent, amphoteric, and poor conductors.

Hydrogen (H2)

Most abundant element; flammable; can behave like Group 1A or 7A element.

Ionic Hydride (NaH)

Metal-hydrogen salt; reacts with water to give NaOH and H2 gas.

Electron-Deficient Boron

Boron often forms 6-electron species that seek additional electron density.

Bridge Bond

Three-center two-electron bond in B2H6 where H bridges two B atoms.

Lewis Acid (BF3)

Electron-pair acceptor; forms adducts such as BF3·NH3.

Diagonal Relationship

Similarity between Be and Al due to small size and high charge density; both amphoteric.

Graphite

Layered sp2 carbon allotrope; conducts electricity.

Graphene

Single sheet of sp2 carbon atoms; extremely strong conductor.

Silicon Dioxide (SiO2)

Network solid showing silicon’s preference for single bonds.

Nitrogen Oxides

Series: N2O(+1), NO(+2), N2O3(+3), NO2/N2O4(+4), N2O5(+5).

Ostwald Process Final Step

3 NO2 + H2O → 2 HNO3 + NO; produces nitric acid industrially.

Contact Process

SO3 + H2O → H2SO4; final step in sulfuric acid manufacture.

Halogen Oxidizing Strength

F2 > Cl2 > Br2 > I2; fluorine is the strongest oxidizer.

Noble Gas Compounds

Only Kr and Xe form stable compounds under normal conditions.

Strongest Reducing Agent (Cs)

Cesium has the greatest tendency to lose an electron in the periodic table.

NaH + H2O Reaction

NaH + H2O → NaOH + H2; hydride reacts, raising pH.

CaCO3 Decomposition

CaCO3 → CaO + CO2; thermal production of lime.

PCl3 Hydrolysis

PCl3 + 3 H2O → H3PO3 + 3 HCl; forms phosphorous acid and HCl.