Chapter 5 Electrons In Atoms 5.1 Revising the Atomic Model 5.2 Electron Arrangement in Atoms 5.3 Atomic Emission Spectra and the Quantum Mechanical Model Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Limitations of Rutherford’s Atomic Model Energy Levels in Atoms Limitations of Rutherford’s Atomic Model It explained only a few simple properties of atoms. It could not explain the chemical properties of elements. For example, Rutherford’s model could not explain why an object such as the iron scroll shown here first glows dull red, then yellow, and then white when heated to higher and higher temperatures. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Energy Levels in Atoms The Bohr Model In 1913, Niels Bohr (1885–1962), a young Danish physicist and a student of Rutherford, developed a new atomic model. He changed Rutherford’s model to incorporate newer discoveries about how the energy of an atom changes when the atom absorbs or emits light. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Energy Levels in Atoms The Bohr Model Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Each possible electron orbit in Bohr’s model has a fixed energy. Energy Levels in Atoms 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. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Energy Levels in Atoms The Bohr Model The rungs on this ladder are somewhat like the energy levels in Bohr’s model of the atom. A person on a ladder cannot stand between the rungs. Similarly, the electrons in an atom cannot exist between energy levels. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Energy Levels in Atoms The Bohr Model The rungs on this ladder are somewhat like the energy levels in Bohr’s model of the atom. The energy levels in atoms are unequally spaced, like the rungs in this unusual ladder. The higher energy levels are closer together. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Bohr’s model is only valid for the first 20 elements Bohr’s model is only valid for the first 20 elements. look at a periodic table Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Let’s build the first 20 elements using our models You need to know some rules Level n = 1 can hold a total of 2 electrons All other levels can hold 8 electrons Take a picture of each completed and labeled atom. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

The Quantum Mechanical Model What does the quantum mechanical model determine about the electrons in an atom? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

The Quantum Mechanical Model The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus of an atom. Areas of probability Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How are the quantum mechanical model and the Bohr model alike How are the quantum mechanical model and the Bohr model alike? How are they different? Like the Bohr model, the quantum mechanical model restricts the energy of electrons to certain values. Unlike the Bohr model, the quantum mechanical model does not specify an exact path the electron takes around the nucleus. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

How do sublevels of principal energy levels differ? Atomic Orbitals Atomic Orbitals How do sublevels of principal energy levels differ? Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Different atomic orbitals are denoted by letters. The s orbitals are spherical. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Different atomic orbitals are denoted by letters. The s orbitals are spherical. The p orbitals are dumbbell-shaped. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atomic Orbitals For a given principal energy level greater than 1, there is one s orbital, 3 p orbitals... Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atomic Orbitals For a given principal energy level greater than 1, there is one s orbital, 3 p orbitals, and 5 d orbitals. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atomic Orbitals Four of the five d orbitals have the same shape but different orientations in space. Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Atomic Orbitals The numbers and types of atomic orbitals depend on the principal energy level. Summary of Principal Energy Levels and Sublevels Principal energy level Number of sublevels Type of sublevel Maximum number of electrons n = 1 1 1s (1 orbital) 2 n = 2 2s (1 orbital), 2p (3 orbitals) 8 n = 3 3 3s (1 orbital), 3p (3 orbitals), 3d (5 orbitals) 18 n = 4 4 4s (1 orbital), 4p (3 orbitals), 4d (5 orbitals), 4f (7 orbitals) 32 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

END OF 5.1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.