Where the spaces mendeleyev left over any use

If you chip a tooth, most likely you will go to the dentist to have the missing material filled in. currently the material used to fill in teeth is a polymer that is flexible when put in, yet is hardened to the strength of a tooth after irradiation with blue light at a wavelength of 461 nm. what is the energy in joules for a photon of light at this wavelength?

Light waves are as they pass through the

Asample of sea water contains 6.28g of sodium chloride per litre of solution. how many milligrams of sodium chloride would be contained in 15.0ml of this solution?