Ununoctium ( or \/ Ë Ê nÉ Ë nÉ ' ktiÉ m \/ ) , also known as eka-radon or element 118 , is the temporary IUPAC name for the transactinide element having the atomic number 118 and temporary element symbol Uuo . Ununoctium is the temporary IUPAC name for the transactinide element having the atomic number 118 and temporary element symbol Uuo .