Q1.
What if … atoms could combine in any ratio and not in a fixed ratio? How would this affect the substances around us?
Answer
Nothing around us would have a reliable identity. Fixed ratios are what make a substance a substance; drop them and chemistry as a science collapses.
- No substance could be named. “Water” would not mean one thing. One sample might be H₂O, another H₃O, another H₁.₄O — each with a different boiling point, density and taste. The word would describe a whole family of liquids, not a compound.
- The Law of Constant Proportions and the Law of Multiple Proportions would both fail, and with them Dalton's fifth postulate. There would be nothing for an atomic theory to explain.
- Chemical formulae, valency and molecular mass would be meaningless. You could not write H₂O, could not calculate a formula unit mass, could not predict how much of one thing reacts with how much of another.
- Medicine would be impossible. A paracetamol tablet works because every molecule in it is identical. If the ratio of atoms drifted from batch to batch, the same tablet could be useless one day and poisonous the next.
- Living things could not exist. Haemoglobin carries oxygen because it has an exact structure; a protein assembled in a random ratio would not fold, would not work, and could not be copied faithfully into the next generation.
Why it happens in the real world: the ratio is fixed because atoms bond to complete their octet, and an octet is a whole number of electrons. Oxygen is short of exactly two electrons, hydrogen of exactly one — so two hydrogens go with one oxygen, never 2.3 of them. Whole numbers in the electron count are what force whole numbers in the formula.