Answer: True
Step-by-step explanation:
A mole is defined as the amount of substance that contains Avogardro number of the substance. Avogadro's number is given by
.

According to avogadro's law, 1 mole of every substance occupies 22.4 Liters at STP and contains avogadro's number
of particles.
Thus the statement saying Avogadro's number is the number of particles in one mole of a pure substance is true.