Simplify the following text for a Grade 9 native English-speaking person.
Original: Thallium ( I ) fluoride ( or thallous fluoride or thallium monofluoride ) is the chemical compound composed of thallium and fluorine with the formula TlF .
Simplified: Thallium ( I ) fluoride , also known as thallous fluoride , is a chemical compound . Its chemical formula is TlF .