Can atoms be divided into smaller pieces

Atoms were thought to be indivisible. They were thought to be the smallest unit. Through various experiments scientists concluded that an atom consists of even smaller particles called sub atomic particles. An atom consists of three subatomic particles namely electrons, protons and neutrons.

answer; i believe the correct answer is (c) /// is a homogeneous mixture of gaseous substance nitrogen,oxygen and smaller amounts of other substancesmixtures can be either ( homogeneous or heterogeneous)plz check first good luck