This document discusses the composition and structure of soil particles. It begins by explaining that soil is composed of solid particles, liquid, and gas that can range in size from boulders to microscopic particles. The solid particles can have various shapes, from spherical to platy or needle-like. Soil mineralogy determines the size, shape, and properties of soil particles, which then influence the physical and chemical properties of the soil. Clays are distinguished from nonclay particles by their small size, negative charge, plasticity, and composition of hydrous aluminum silicates. The document then discusses the atomic structure and bonding within soil minerals.