The ion SeO4^2-, known as selenate, is a negatively charged polyatomic ion composed of one selenium atom and four oxygen atoms. It carries a -2 charge, which means it has two more electrons than protons. Selenate is commonly found in various chemical compounds and plays a role in environmental chemistry, particularly in the context of selenium's behavior in soil and water. Selenate is often used in laboratory settings and can be a source of selenium in biological systems. It is important for certain organisms, as selenium is an essential trace element. However, excessive levels of selenate can be toxic, highlighting the need for careful management in agricultural and industrial applications.