© Copyright Pearson Prentice Hall Slide 1 of 26 Light and Atoms. 5.1

© Copyright Pearson Prentice Hall Models of the Atom > Slide 2 of 26 The Development of Atomic Models What was inadequate about Rutherford’s atomic model? 5.1

Slide 3 of 26 © Copyright Pearson Prentice Hall Models of the Atom > The Development of Atomic Models Rutherford’s atomic model could not explain the chemical properties of elements. Rutherford’s atomic model could not explain why objects change color when heated. 5.1

Slide 4 of 26 © Copyright Pearson Prentice Hall Models of the Atom > The Development of Atomic Models The timeline shows the development of atomic models from 1913 to

Slide 5 of 26 © Copyright Pearson Prentice Hall Models of the Atom > Bohr’s model Electrons orbit the nucleus in “shells” Electrons can be bumped up to a higher shell if hit by an electron or a photon of light. Bohr Model

Slide 6 of 38 © Copyright Pearson Prentice Hall Physics and the Quantum Mechanical Model > Light According to the wave model, light consists of electromagnetic waves. Electromagnetic radiation includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays. All electromagnetic waves travel in a vacuum at a speed of  10 8 m/s. 5.3

Slide 7 of 38 © Copyright Pearson Prentice Hall Physics and the Quantum Mechanical Model > Light According to the wave model, light consists of electromagnetic waves. Electromagnetic radiation includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays. All electromagnetic waves travel in a vacuum at a speed of  10 8 m/s. 5.3

Slide 8 of 38 © Copyright Pearson Prentice Hall Physics and the Quantum Mechanical Model > Light The electromagnetic spectrum consists of radiation over a broad band of wavelengths. 5.3

© Copyright Pearson Prentice Hall Physics and the Quantum Mechanical Model > Slide 9 of 38 Atomic Spectra What causes atomic emission spectra? 5.3

© Copyright Pearson Prentice Hall Slide 10 of 38 Physics and the Quantum Mechanical Model > Atomic Spectra When atoms absorb energy, electrons move into higher energy levels. These electrons then lose energy by emitting light when they return to lower energy levels. 5.3

Slide 11 of 38 © Copyright Pearson Prentice Hall Physics and the Quantum Mechanical Model > Atomic Spectra A prism separates light into the colors it contains. When white light passes through a prism, it produces a rainbow of colors. 5.3

Slide 12 of 38 © Copyright Pearson Prentice Hall Physics and the Quantum Mechanical Model > Atomic Spectra When light from a helium lamp passes through a prism, discrete lines are produced. 5.3

© Copyright Pearson Prentice Hall Models of the Atom > Slide 13 of 26 The Bohr Model What was the new proposal in the Bohr model of the atom? 5.1

© Copyright Pearson Prentice Hall Slide 14 of 26 Models of the Atom > The Bohr Model Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus. 5.1

Slide 15 of 26 © Copyright Pearson Prentice Hall Models of the Atom > The Bohr Model Each possible electron orbit in Bohr’s model has a fixed energy. The fixed energies an electron can have are called energy levels. A quantum of energy is the amount of energy required to move an electron from one energy level to another energy level. 5.1

Slide 16 of 26 © Copyright Pearson Prentice Hall Models of the Atom > The Bohr Model Like the rungs of the strange ladder, the energy levels in an atom are not equally spaced. The higher the energy level occupied by an electron, the less energy it takes to move from that energy level to the next higher energy level. 5.1

Slide 17 of 26 © Copyright Pearson Prentice Hall Models of the Atom > The Quantum Mechanical Model Austrian physicist Erwin Schrödinger (1887– 1961) used new theoretical calculations and results to devise and solve a mathematical equation describing the behavior of the electron in a hydrogen atom. The modern description of the electrons in atoms, the quantum mechanical model, comes from the mathematical solutions to the Schrödinger equation. 5.1

Slide 18 of 26 © Copyright Pearson Prentice Hall Models of the Atom > The Quantum Mechanical Model The propeller blade has the same probability of being anywhere in the blurry region, but you cannot tell its location at any instant. The electron cloud of an atom can be compared to a spinning airplane propeller. 5.1

Slide 19 of 26 © Copyright Pearson Prentice Hall Models of the Atom > The Quantum Mechanical Model In the quantum mechanical model, the probability of finding an electron within a certain volume of space surrounding the nucleus can be represented as a fuzzy cloud. The cloud is more dense where the probability of finding the electron is high. 5.1

© Copyright Pearson Prentice Hall Models of the Atom > Slide 20 of 26 Atomic Orbitals How do sublevels of principal energy levels differ? 5.1

Slide 21 of 26 © Copyright Pearson Prentice Hall Models of the Atom > Atomic Orbitals An atomic orbital is often thought of as a region of space in which there is a high probability of finding an electron. Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found. 5.1

Slide 22 of 26 © Copyright Pearson Prentice Hall Models of the Atom > Atomic Orbitals Different atomic orbitals are denoted by letters. The s orbitals are spherical, and p orbitals are dumbbell-shaped. 5.1

Slide 23 of 26 © Copyright Pearson Prentice Hall Models of the Atom > Atomic Orbitals Four of the five d orbitals have the same shape but different orientations in space. 5.1

Slide 24 of 26 © Copyright Pearson Prentice Hall Models of the Atom > Atomic Orbitals The numbers and kinds of atomic orbitals depend on the energy sublevel. 5.1

Slide 25 of 26 © Copyright Pearson Prentice Hall Models of the Atom > Atomic Orbitals The number of electrons allowed in each of the first four energy levels are shown here. 5.1