Bohr Model Of Atom

Spectrum Continuous spectrum is the rainbow of colors containing all wavelengths Line spectrum contains only certain colors or wavelengths When gases are given energy, they emit line spectra which are characteristic of that gas

Continuous Spectrum Line Spectrum of Hydrogen

Niels Bohr Said electrons occupy the atoms in quantized energy levels Each level (orbit) is assigned an integer (n) called the principal quantum number As n increases, the radius of orbit is greater

Energy Energy of the electron depends on the level it occupies En = - RH ( 1/n2) RH is called the Rydberg constant RH = 2.18x10-18 J

Coulomb’s Law The energy comes from the potential energy resulting from a separation between a positive and negative charge Coulomb’s law describes this q1 and q2 are the two charges r is the distance between the charges k = 2.31 x 10-19

When electrons occupy the lowest possible energy level, they are in ground state When in higher levels, they are in excited state

Hydrogen Line Spectrum H atom absorb a quantum of energy Energized electron “jumps” to a higher level When it falls back down, it gives off energy as a photon of light The frequency of the light depends on the levels it falls from and to

Equation ΔE = Ef – Ei hν = RH ( 1/nf2 - 1/ni2) frequency of light given off depends on the level transition

Example 1 Calculate the frequency and wavelength of light given off when an electron in a H atom falls from n=4 to n=2. What color is it?

Ionization of Energy Energy that would be needed to completely remove the electron; make it go from n = 1 to n = ∞

Example 2 Calculate the energy required to ionize an electron from the ground state.