Cations are positively charged ion while anions are negatively charged ions formed by loosing and gaining of electrons respectively. Transition metals are metals in the middle of the periodic table with multiple oxidation states. The charge on the transition metal is equal to the oxidation state which varies from +1 to +7. The charge of transition metal can also be determined in neutral compound as long as one knows the charge or the oxidation state of the other atom in the compound. The charge of transition can also be determined in the case of neutral complexes where the transition element has combined with other atoms to form molecular complexes that are either positively or negatively charged, e.g. MnO4-. Lastly Neutral transition metal compounds which are soluble in water have a charge of +3 or less than+3.
Photoreceptors are a sensor that is connected to your retina. They sense light and send the message to your brain. The sensors automatically squint your eyes if something will blind you.
