The Bohr Model of the Atom I Bohr’s model was a ‘patchwork’ of classical physics and the new idea classical physics and the new idea of quanta of quanta It was the first to be able to explain the interaction of matter and light at the interaction of matter and light at the atomic level; it gave a theoretical basis atomic level; it gave a theoretical basis to Balmer / Rydberg’s empirical equation to Balmer / Rydberg’s empirical equation It was based on several postulates that allowed the calculation of the energy and allowed the calculation of the energy and wavelength of light absorption / emission wavelength of light absorption / emission
The Bohr model did have some limitations: It provides no explanation for why the It provides no explanation for why the electrons energy was quantized electrons energy was quantized It doesn’t work with any atom / ion having more than 1 electron It doesn’t work with any atom / ion having more than 1 electron It holds onto the classical idea of precise pathways along which the electron moves It holds onto the classical idea of precise pathways along which the electron moves The Bohr Model of the Atom II
The Nature of the Electron, Revisited de Broglie offered an idea which provided a way to overcome one of the limitations of Bohr’s model – the quantized nature of the energy levels: the limitations of Bohr’s model – the quantized nature of the energy levels: If light can exhibit particle-like properties, why can’t electrons exhibit wave-like properties? Davisson & Germer obtainedexperi-mentalproof
So, What Is the Electron – Particle or Wave? Our modern understanding says it is neither... until you observe it!
“Do you believe in fate, Neo?” Out with the old, concrete model...... in with the new, cloudy model... You must sacrifice predictability...... for a less certain probability.
The Property of Ionization Energy Ionization energy is the energy to remove an electron from a neutral atom or ion What things affect the ionization energy for a particular atom / ion? 1.C harge 2.D istance As would be predicted by Coulomb’s Law F = k e x q1 x q2q1 x q2q1 x q2q1 x q2 r2r2r2r2
Element I.E. G. 1 I.E. G. 2 I.E. G. 3 I.E. G. 4 I.E. G. 5 I.E. G. 6 I.E. G. 7 H1.31 He2.37 Li6.260.52 Be11.50.90 B19.31.360.80 C28.61.721.09 N39.62.451.40 O52.63.041.31 F67.23.881.68 Ne84.04.682.08 Na1046.843.670.50 Mg1269.075.310.74 Al15112.17.191.090.58 Si178184.108.40.2060.79 P20818.713.51.951.06 S23922.716.52.051.00 Cl27326.820.22.441.25 Ar30931.524.12.821.52 K347220.127.116.112.380.42 Ca39042.734.04.652.900.59 Sc43348.539.25.443.240.770.63
The Stern-Gerlach Experiment and the 4 th Quantum Number This experiment lead to the identification of two quantized spin states for the electron -- + 1 / 2 quantized spin states for the electron -- + 1 / 2 and - 1 / 2 – and the spin quantum number (m s ) and - 1 / 2 – and the spin quantum number (m s )
Superatoms The team used photoelectron imaging spectroscopy to examine similarities between a nickel atom and a titanium- monoxide molecule. Left: Graphical displays of energy peaks were similar between a nickel atom and a titanium- monoxide molecule. Right: Bright spots in the images, which correspond to the energy of the electrons emitted during their removal from the atoms' outer shells, appeared to be similar between a nickel atom (right, top) and a titanium- monoxide molecule (right, bottom). (Credit: Castleman lab, Penn State)
Why Are Super-Atoms of Interest? VCs 8 and MnAu 24 (SH) 18 magnetic superatoms that mimic a manganese atom. The MnAu 24 cluster is surrounded by sulfur and hydrogen atoms to protect it against outside attack, thus making it valuable for use in biomedical applications. (Credit: Image courtesy of Ulises Reveles, Ph.D, VCU.)