Hydrogen (supplementary)
Class 11 · Updated 2026-10-03. Published for practice.
Hydrogen’s odd place
Supplementary note: some CBSE Class 11 schedules no longer examine this full chapter. Use only if your school still teaches it.
Hydrogen has one electron like alkali metals but forms covalent hydrides like halogens. NCERT places it separately: resemblance to Group 1 (losing one electron → H+) and Group 17 (gaining one electron → H-).
Isotopes: protium 1H, deuterium 2H (D), tritium 3H (radioactive). Heavy water is D2O. Isotopes differ in mass and some reaction rates; chemistry is largely similar except where mass matters (kinetic isotope effects).
How H₂ is made in the syllabus
Lab routes you should recognise: zinc + dilute acid; reaction of metals with bases (some syllabus variants); electrolysis of water.
Industrial scale: steam reforming of methane and related processes — know that most bulk H2 is not from test-tube Zn + HCl.
Hydrogen as a fuel idea: clean burn to water, but storage and production energy remain engineering challenges beyond the textbook.
Hydrides
Ionic (saline) hydrides: H- with highly electropositive metals (NaH, CaH2). Covalent hydrides: most p-block elements (CH4, NH3, H2O, HF). Metallic hydrides: transition metals absorb H (non-stoichiometric often).
Water: amphoteric behaviour is not the headline — polarity, hydrogen bonding, and high heat capacity are. Hard water vs soft water: Ca2+/Mg2+ salts cause hardness; temporary hardness can be removed by boiling (carbonate precipitation).
Hydrogen peroxide H2O2: pale blue liquid; non-planar (open book) structure; acts as oxidising and reducing agent (disproportionates to H2O and O2, especially with catalysts or on standing).