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Wavelike properties of electrons help relate atomic emission spectra, energy states of atoms, and atomic orbitals. Section 2: Quantum Theory and the Atom K What I Know W What I Want to Find Out L What I Learned

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6(A) Understand the experimental design and conclusions used in the development of modern atomic theory, including Daltons Postulates, Thomsons discovery of electron properties, Rutherfords nuclear atom, and Bohrs nuclear atom. 6(C) Calculate the wavelength, frequency, and energy of light using Planck's constant and the speed of light. 3(F) Research and describe the history of chemistry and contributions of scientists. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Essential Questions How do the Bohr and quantum mechanical models of the atom compare? What is the impact of de Broglies wave-particle duality and the Heisenberg uncertainty principle on the current view of electrons in atoms? Quantum Theory and the Atom Copyright McGraw-Hill Education

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Review atom New ground state quantum number de Broglie equation Heisenberg uncertainty principle quantum mechanical model of the atom atomic orbital principal quantum number principal energy level energy sublevel Quantum Theory and the Atom Copyright McGraw-Hill Education Vocabulary

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Bohrs Model of the Atom Einsteins theory of lights dual nature accounted for several unexplainable phenomena but not why atomic emission spectra of elements were discontinuous rather continuous. In 1913, Niels Bohr, a Danish physicist working in Rutherfords laboratory, proposed a quantum model for the hydrogen atom that seemed to answer this question. Bohr correctly predicted the frequency lines in hydrogens atomic emission spectrum. The lowest allowable energy state of an atom is called its ground state. When an atom gains energy, it is in an excited state. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Bohrs Model of the Atom Bohr suggested that an electron moves around the nucleus only in certain allowed circular orbits. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Bohrs Model of the Atom Each orbit was given a number, called the quantum number. Hydrogens single electron is in the n = 1 orbit in the ground state. When energy is added, the electron moves to the n = 2 orbit. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Bohrs Model of the Atom Quantum Theory and the Atom Copyright McGraw-Hill Education

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The Balmer Series Concepts in Motion FPO Add link to concepts in motion animation from page 147 here. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Electron Transitions Energy levels are similar to the rungs of a ladder. The four visible lines correspond to electrons dropping from a higher n to the orbit n = 2. As n increases, the hydrogen atoms energy levels are closer to each other. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Electron Transitions Concepts in Motion FPO Add link to concepts in motion animation from page 148 here. Quantum Theory and the Atom Copyright McGraw-Hill Education

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The Limits of Bohrs Model Bohrs model explained the hydrogens spectral lines, but failed to explain any other elements lines. The behavior of electrons is still not fully understood, but substantial evidence indicates they do not move around the nucleus in circular orbits. Quantum Theory and the Atom Copyright McGraw-Hill Education

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The Quantum Mechanical Model of the Atom Louis de Broglie (18921987) hypothesized that particles, including electrons, could also have wavelike behaviors. The figure illustrates that electrons orbit the nucleus only in whole-number wavelengths. Quantum Theory and the Atom Copyright McGraw-Hill Education

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The Quantum Mechanical Model of the Atom The de Broglie equation predicts that all moving particles have wave characteristics. Quantum Theory and the Atom Copyright McGraw-Hill Education

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The Quantum Mechanical Model of the Atom Heisenberg showed it is impossible to take any measurement of an object without disturbing it. The Heisenberg uncertainty principle states that it is fundamentally impossible to know precisely both the velocity and position of a particle at the same time. The only quantity that can be known is the probability for an electron to occupy a certain region around the nucleus. Quantum Theory and the Atom Copyright McGraw-Hill Education

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The Quantum Mechanical Model of the Atom Schrdinger treated electrons as waves in a model called the quantum mechanical model of the atom. Schrdingers equation applied equally well to elements other than hydrogen. The wave function predicts a three- dimensional region around the nucleus called the atomic orbital. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Hydrogen Atomic Orbitals Principal quantum number (n) indicates the relative size and energy of atomic orbitals. n specifies the atoms major energy levels, called the principal energy levels. Energy sublevels are contained within the principal energy levels. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Fireworks Concepts in Motion FPO Add link to video from page 153 here. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Hydrogen Atomic Orbitals Each energy sublevel relates to orbitals of different shape. Quantum Theory and the Atom Copyright McGraw-Hill Education

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Hydrogen Atomic Orbitals Quantum Theory and the Atom Copyright McGraw-Hill Education

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Quantum Theory and the Atom Copyright McGraw-Hill Education Review Essential Questions How do the Bohr and quantum mechanical models of the atom compare? What is the impact of de Broglies wave-particle duality and the Heisenberg uncertainty principle on the current view of electrons in atoms? Vocabulary ground state quantum number de Broglie equation Heisenberg uncertainty principle quantum mechanical model of the atom atomic orbital principal quantum number principal energy level energy sublevel