Why don't the halogens bond with other groups

Can someone me with 1 to 4 plz. fast

Compare and contrast the bohr model and the electron cloud models of the atom.

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?