Compound reference
Formaldehyde
CH₂O
The chemistry
One double bond and two single bonds on one carbon. Same atom, three different neighbors, three regions of electron density → flat triangle.
Remember it as…
O=C(–H)(–H). The double bond and two singles all count as one region each. Three groups → trigonal planar.
Common mix-up
Mixed bond orders do NOT change the VSEPR count. Carbon in CH₂O has one double + two singles = 3 electron groups (not 4). Three groups → trigonal planar at ~120°, not tetrahedral.
Where the name comes from
Form- from Latin formica (ant) - formic acid is what makes an ant bite sting. Formaldehyde is the aldehyde of formic acid (one less O, one more H).
Where you meet it
Embalming fluid; precursor to plastics (Bakelite, melamine); the simplest carbonyl group, a chemical motif present in every fat, sugar, and protein.
PubChem facts
- IUPAC name
- formaldehyde
- Molecular weight
- 30.026 g/mol
Also known as: methanal, formalin (the water solution), formol
Handling note
Toxic, corrosive, and a known carcinogen, handled only with care and ventilation.
BondingMolecular geometry
Chemical data from PubChem (NIH/NCBI)