Glossary — INC-03 Key Terms — Notes

Term	Definition
Contact process	Industrial 4-step method for manufacturing H2SO4 using V2O5 catalyst at 450°C
Oleum (fuming H2SO4)	H2S2O7 (pyrosulfuric acid) — formed when SO3 is dissolved in concentrated H2SO4
Acid mist	Fine aerosol of H2SO4 droplets formed when SO3 reacts directly with water — too fine to condense
Chalcogens	Group 16 elements: O, S, Se, Te, Po — named from Greek "chalcos" (copper ore)
Halogens	Group 17 elements: F, Cl, Br, I, At — named from Greek "hals" (salt) + "gen" (producer)
Noble gases	Group 18 elements: He, Ne, Ar, Kr, Xe, Rn — very low reactivity, complete valence shells
Interhalogen compounds	Compounds formed between two different halogens. Formula: ABn (n = 1, 3, 5, 7)
Hybridization	Mixing of atomic orbitals to form new hybrid orbitals of equivalent energy for bonding
sp3d hybridization	Mixing of 1s + 3p + 1d orbital → 5 hybrid orbitals → TBP electron geometry
sp3d2 hybridization	Mixing of 1s + 3p + 2d orbitals → 6 hybrid orbitals → Octahedral electron geometry
sp3d3 hybridization	Mixing of 1s + 3p + 3d orbitals → 7 hybrid orbitals → Pentagonal bipyramidal geometry
VSEPR theory	Valence Shell Electron Pair Repulsion — predicts molecular shape based on electron pair repulsions
Diprotic acid	Acid that can donate 2 protons per molecule (e.g., H2SO4)
Allotropes	Different physical forms of the same element (e.g., rhombic and monoclinic sulfur)
Rhombic sulfur	Most stable sulfur allotrope at room temperature; consists of S8 crown-shaped rings; orthorhombic crystal
Clathrate compound	"Cage compound" where noble gas atoms are physically trapped in lattice of water/organic molecules without chemical bonding
Nascent oxygen	Highly reactive atomic oxygen [O] released by decomposition of O3 → O2 + [O]
Bleaching powder	CaOCl2 — mixed salt of HCl and HOCl, prepared by Cl2 + Ca(OH)2
Resonance hybrid	A molecule whose actual structure is an average of two or more contributing structures (e.g., O3, SO2)
Sulfonating agent	Reagent that introduces -SO3H group into organic molecules (e.g., H2SO4 in aromatic sulfonation)
KI-starch paper	Test paper used to detect oxidizing agents (O3, Cl2); turns blue-black when I2 is liberated