Non-metallic oxides are compounds formed by the reaction of oxygen with non-metal elements. These oxides typically include substances like carbon dioxide (CO₂), water (H₂O), and sulfur dioxide (SO₂). They are generally characterized by their covalent bonding and can exist in various states, such as gases, liquids, or solids, depending on temperature and pressure. These oxides play significant roles in both nature and industry. For example, carbon dioxide is essential for photosynthesis in plants, while sulfur dioxide is often used in the production of sulfuric acid. Non-metallic oxides can also contribute to environmental issues, such as acid rain.