In the ClO4- ion perchlorate ion , the chlorine atom is the central atom surrounded by four oxygen atoms. To determine the hybridization of the chlorine atom, we need to consider its electron domains.Chlorine has 7 valence electrons, and in ClO4-, it forms one single bond with each of the four oxygen atoms. Additionally, there is one extra electron from the negative charge on the ion. So, chlorine has a total of 7 + 1 = 8 electrons in its valence shell.These 8 electrons are distributed in 4 electron domains 4 single bonds with oxygen atoms . To accommodate these 4 electron domains, the chlorine atom needs to use one s orbital, two p orbitals, and one d orbital. Therefore, the hybridization of the chlorine atom in ClO4- is sp3d.