What Is the energy of a photon with a wavelength of 21nm? I

The energy of a photon with a wavelength of 350 nm is 5.7×10−19 J.

since the atomic number is the number of protons in the nucleus, as we move to the left on the periodic table, the electrostatic pull between the nucleus and the valence electron shell decreases. as we move down a group (vertical column), the valence shell energy level gets further and further from the nucleus.

1. they vary with a higher number because boiling is way hotter than melting