Which one of the following is considered to be the smallest particulate matter?

AFine mode particles

BNucleation mode particles ✓ Correct

CAitken mode particles

DAccumulation mode particles

Correct answer: (B) Nucleation mode particles

Explanation

Nucleation mode particles are the smallest particulate matter, formed by fresh condensation of vapours.

They quickly grow or clump, so they are short-lived in the air.

Fine mode covers a broad small-size class but is larger than the nucleation particles.

Aitken mode particles are larger than nucleation mode ones.

Accumulation mode particles are larger still, built up by coagulation and growth.

Nucleation mode particles are typically below about 10 nanometres across.

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