Question

Ionization involves completely removing an electron from an atom. light of a particular wavelength can cause ionization to occur if it has the required energy. the energy to ionize a certain element is 342 kj/mol. what wavelength contains enough energy in a single photon to ionize one atom of this element?

Answer 1

350 nanometers We first need to calculate how much energy is needed to ionize a single atom. So divide the kilojoules/mol energy value by avogadro's number. 342 kj/mol / 6.0221409x10^23 = 5.67904x10^-19 Joules So we need a photon with 5.67904x10^-19 Joules of energy. The equation to express the energy of a photon is E = hc/w where h = Planck constant (6.626070040Ă—10â’34 Js) c = speed of light (299792458 m/s) w = wavelength of photon Solving for w E = hc/w Ew = hc w = hc/E Substituting known values w = 6.626070040Ă—10^â’34 Js * 299792458 m/s / 5.67904x10^-19 J w = 1.9864458x10^-25 Jm / 5.67904x10^-19 J w = 3.497855x10^-7 m w = 3.50x10^-7 m w = 350 nm