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 processes. These compounds are typically soluble in water and can act as weak bases. They play important roles in agriculture, helping to provide essential nutrients to plants. Additionally, ammonium compounds are used in household cleaning products and as food additives, highlighting their versatility in everyday applications.