Name three elements that have similar chemical properties to oxygen

Elements that will have similar properties to oxygen will be the one present in its own group. these include sulphur, selenium and tellurium. all of them form x⁻² ion, showing that they would chemically react in a similar way and hence similar chemical properties. moreover, the groups in periodic table are formed to group elements with similar chemical properties

The answer is water molecules are split.cellular respiration and photosynthesis are complement  reactions to each other. these are reverse reactions. in cellular respiration glucose and oxygen yield water and carbon dioxide. so, when respiration begins,  glucose molecules are split. in the opposite reaction - in photosynthesis, carbon dioxide and water yield glucose and oxygen. thus,  when respiration begins, water molecules are split.