What is two of same elements is called

Explain which atom l or m is more stable and why

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 ph of a solution that has a hydrogen ion concentration of 1.0 * 10 -9 m?