Structure of Atom — Introduction

An atom is the smallest unit of an element that takes part in chemical reactions. Although atoms are very small, they are made of even smaller particles called subatomic particles.

• ›Main particles: electron, proton, neutron.
• ›Atom is usually electrically neutral.
• ›Protons and neutrons are present in the nucleus.
• ›Electrons move around the nucleus in shells or energy levels.

This topic is important because it explains why elements react, form ions, and take fixed places in the periodic table.