Ammonium compounds are chemical substances that contain the ammonium ion, NH4+. These compounds are formed when ammonia, a gas with the formula NH3, reacts with acids. Common examples include ammonium chloride and ammonium sulfate, which are often used in fertilizers and various industrial applications. These compounds are typically soluble in water and can act as weak bases. They play a significant role in agriculture, helping to provide essential nutrients to plants. Additionally, ammonium compounds are used in cleaning products and as food additives, showcasing their versatility in everyday life.