In the compound HClO4 perchloric acid , the oxidation state of chlorine can be determined by considering the oxidation states of the other atoms in the compound and the overall charge of the compound.The oxidation state of hydrogen H is +1, and the oxidation state of oxygen O is -2. Since there are four oxygen atoms, the total oxidation state for oxygen is -8. The compound HClO4 is neutral, so the sum of the oxidation states of all the atoms must be zero.Let x be the oxidation state of chlorine Cl . Then, the equation for the sum of the oxidation states is: +1 + x + -8 = 0Solving for x:x - 7 = 0x = +7So, the oxidation state of chlorine in the compound HClO4 is +7.