Warm-Up Use the information below to answer the following questions: λ = wavelength ν = frequency c = λν E = hν c = 3.00 x 108 m/s h = 6.63 x 10-34 J/Hz What is the frequency of an ultraviolet wave with a wavelength of 1.20 x 10-9 m? What is the energy of the wave in #1?

Warm-Up Use the information below to answer the following questions: λ = wavelength ν = frequency c = λν E = hν c = 3.00 x 108 m/s h = 6.63 x 10-34 J/Hz What is the frequency of an ultraviolet wave with a wavelength of 1.20 x 10-9 m?

Warm-Up Use the information below to answer the following questions: λ = wavelength ν = frequency c = λν c = 3.00 x 108 m/s What is the frequency of an ultraviolet wave with a wavelength of 1.20 x 10-9 m?

Warm-Up Use the information below to answer the following questions: λ = wavelength ν = frequency c = λν E = hν c = 3.00 x 108 m/s h = 6.63 x 10-34 J/Hz 2) What is the energy of the wave in #1? (ν = 2.5 x 10^17 Hz)

Modern atomic structure

Evolution of the Atom

The Bohr Model Electron circles the nucleus in allowed orbitals with a fixed radius Lowest energy orbital is the smallest and is closest to the nucleus

Energy Levels Energy levels are quantized Electrons can step up to a higher energy level or down to a lower energy level (but not in between) When electrons are as close to the nucleus as they can be, they are in the ground state. When they are anywhere else, they are in an excited state. Each atom has only one ground state, but many excited states

Spectral Lines Electrons fall from an excited energy state to a lower energy state and emit a photon with a specific energy:

Energy of Electrons Bohr was able to calculate the energy that an electron would have in the different energy levels for the hydrogen atom. This let him account for the spectral lines!

What wavelength of light is emitted when an electron falls from the 2nd energy level to the 1st energy level? What energy does this photon have? c = λν c = 3.00 x 108 m/s E = hν h = 6.63 x 10-34 J/Hz

Pros & Cons Accuracy Limitations Explains hydrogen’s spectral lines very well Idea of quantized energy levels paved the path for future research Could not explain the spectral lines of atoms with more than one electron (all except hydrogen)

Spectroscopy By studying the emission spectrum of a certain substance, the identity of the atoms in the substance can be determined. We call this unique series of lines the atom’s fingerprint. Instrument used: spectrometer

Warm-Up What type of EM radiation is emitted with an electron transition from n=4 to n=3? What is the wavelength of a photon emitted as a result of an electron transition from n=2 to n=1? What color of light is emitted when an electron falls from n=3 to n=2? What color of light is emitted when an electron falls from n=4 to n=2?