Q.Compare the structures of H2O and H2O2.

Structure of H2O:

• Water has a simple, angular (bent) molecular shape.
• Oxygen is $sp^3$ hybridised, with 2 bond pairs (to the 2 H atoms) and 2 lone pairs.
• The H–O–H bond angle is approximately 104.5° (slightly less than the ideal tetrahedral 109.5° due to greater lone pair–lone pair repulsion).
• O–H bond length ≈ 95.7 pm.

Structure of H2O2:

• Hydrogen peroxide has a more complex, non-planar "open book" (skew) structure.
• It contains a central O–O single bond (the peroxide linkage), with one O–H bond attached to each oxygen.
• Each oxygen is $sp^3$ hybridised (2 lone pairs + 2 bond pairs each).
• Unlike water, the two O–H bonds do not lie in the same plane — the molecule can be visualised as two pages of a partly-opened book hinged along the O–O bond, with the two O–H bonds twisted relative to each other by a dihedral angle (~90.2° in the gas phase; ~111.5° in the solid state).
• O–O bond length ≈ 148 pm; O–H bond length ≈ 97 pm; the O–O–H bond angle is ≈ 94.8° (gas)/101.9° (solid). …

Describe H2O's simple bent geometry (sp3 O, 104.5°) first, then build up H2O2's structure from an O–O bond with an O–H attached to each O, noting the non-planar " …

• Drawing/describing H2O2 as planar — its defining structural feature is that it is NON-planar (open-book/skew). …