Metric Conversions 200 m=__km

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?

What is the empirical formula of c6h18o3? ch3o c2h5o c2h6o c2h5o5

Which element would mostly likely have an electron affinity measuring closest to zero