Electron arrangement in atoms
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Rules for determining how electrons fill their energy levels.
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Electron arrangement in atoms
- 1. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Chapter 5 Electron Arrangement in Atoms
- 2. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 2 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. What are the three rules for writing the electron configurations of elements? Electron Configurations Electron ConfigurationsElectron Configurations
- 3. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 3 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. The ways in which electrons are arranged in various orbitals around the nuclei of atoms are called electron configurations. Electron ConfigurationsElectron Configurations
- 4. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 4 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Three rules—the aufbau principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms. Electron ConfigurationsElectron Configurations
- 5. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 5 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Aufbau Principle Electron ConfigurationsElectron Configurations According to the aufbau principle, electrons occupy the orbitals of lowest energy first. In the aufbau diagram, each box represents an atomic orbital. Increasingenergy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p
- 6. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 6 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Aufbau Principle Electron ConfigurationsElectron Configurations Increasingenergy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p The aufbau diagram shows the relative energy levels of the various atomic orbitals. Orbitals of greater energy are higher on the diagram.
- 7. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 7 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Aufbau Principle Electron ConfigurationsElectron Configurations Increasingenergy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p The range of energy levels within a principal energy level can overlap the energy levels of another principal level.
- 8. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 8 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Pauli Exclusion Principle • According to the Pauli exclusion principle, an atomic orbital may describe at most two electrons. • To occupy the same orbital, two electrons must have opposite spins; that is, the electron spins must be paired. Electron ConfigurationsElectron Configurations
- 9. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 9 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Pauli Exclusion Principle • Spin is a quantum mechanical property of electrons and may be thought of as clockwise or counterclockwise. • A vertical arrow indicates an electron and its direction of spin (↑ or ↓). • An orbital containing paired electrons is written as . Electron ConfigurationsElectron Configurations
- 10. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 10 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Hund’s Rule According to Hund’s rule, electrons occupy orbitals of the same energy in a way that makes the number of electrons with the same spin direction as large as possible. Electron ConfigurationsElectron Configurations
- 11. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 11 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Hund’s Rule Three electrons would occupy three orbitals of equal energy as follows. Electron ConfigurationsElectron Configurations
- 12. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 12 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Hund’s Rule Three electrons would occupy three orbitals of equal energy as follows. Electrons then occupy each orbital so that their spins are paired with the first electron in the orbital. Electron ConfigurationsElectron Configurations
- 13. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 13 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Electron ConfigurationsElectron Configurations Look at the orbital filling diagram of the oxygen atom. Electron Configurations of Selected Elements Element 1s 2s 2px 2py 2pz 3s Electron configuration H 1s1 He 1s2 Li 1s2 2s1 C 1s2 2s2 2p2 N 1s2 2s2 2p3 O 1s2 2s2 2p4 F 1s2 2s2 2p5 Ne 1s2 2s2 2p6 Na 1s2 2s2 2p6 3s1 • An oxygen atom contains eight electrons.
- 14. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 14 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Electron ConfigurationsElectron Configurations Look at the orbital filling diagram of the oxygen atom. Electron Configurations of Selected Elements Element 1s 2s 2px 2py 2pz 3s Electron configuration H 1s1 He 1s2 Li 1s2 2s1 C 1s2 2s2 2p2 N 1s2 2s2 2p3 O 1s2 2s2 2p4 F 1s2 2s2 2p5 Ne 1s2 2s2 2p6 Na 1s2 2s2 2p6 3s1 • The 1s orbital has two electrons of opposite spin.
- 15. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 15 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Electron ConfigurationsElectron Configurations Look at the orbital filling diagram of the oxygen atom. Electron Configurations of Selected Elements Element 1s 2s 2px 2py 2pz 3s Electron configuration H 1s1 He 1s2 Li 1s2 2s1 C 1s2 2s2 2p2 N 1s2 2s2 2p3 O 1s2 2s2 2p4 F 1s2 2s2 2p5 Ne 1s2 2s2 2p6 Na 1s2 2s2 2p6 3s1 • The 1s orbital has two electrons of opposite spin. • The 2s orbital also has two electrons of opposite spin.
- 16. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 16 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Electron ConfigurationsElectron Configurations Look at the orbital filling diagram of the oxygen atom. • Each of the three 2p orbitals has one electron. The remaining electron now pairs with an electron occupying one of the 2p orbitals. Electron Configurations of Selected Elements Element 1s 2s 2px 2py 2pz 3s Electron configuration H 1s1 He 1s2 Li 1s2 2s1 C 1s2 2s2 2p2 N 1s2 2s2 2p3 O 1s2 2s2 2p4 F 1s2 2s2 2p5 Ne 1s2 2s2 2p6 Na 1s2 2s2 2p6 3s1
- 17. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 17 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. • A convenient shorthand method for showing the electron configuration of an atom involves writing the energy level and the symbol for every sublevel occupied by an electron. Electron ConfigurationsElectron Configurations
- 18. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 18 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. • A convenient shorthand method for showing the electron configuration of an atom involves writing the energy level and the symbol for every sublevel occupied by an electron. • You indicate the number of electrons occupying that sublevel with a superscript. Electron ConfigurationsElectron Configurations
- 19. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 19 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. • For hydrogen, with one electron in a 1s orbital, the electron configuration is written 1s1 . Electron ConfigurationsElectron Configurations
- 20. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 20 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. • For hydrogen, with one electron in a 1s orbital, the electron configuration is written 1s1 . • For oxygen, with two electrons in a 1s orbital, two electrons in a 2s orbital, and four electrons in 2p orbitals, the electron configuration is 1s2 2s2 2p4 . Electron ConfigurationsElectron Configurations
- 21. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 21 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. • For hydrogen, with one electron in a 1s orbital, the electron configuration is written 1s1 . • For oxygen, with two electrons in a 1s orbital, two electrons in a 2s orbital, and four electrons in 2p orbitals, the electron configuration is 1s2 2s2 2p4 . Electron ConfigurationsElectron Configurations Note that the sum of the superscripts equals the number of electrons in the atom.
- 22. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 22 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 5.1Sample Problem 5.1 Analyze Identify the relevant concepts. Phosphorus has 15 electrons. There is a maximum of two electrons per orbital. Electrons do not pair up within an energy sublevel (orbitals of equal energy) until each orbital already has one electron. 1 When writing electron configurations, the sublevels within the same principal energy level are written together.
- 23. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 23 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 5.1Sample Problem 5.1 Solve Apply the concepts to this problem. • Use the aufbau diagram to place electrons in the orbital with the lowest energy (1s) first. 2 1s
- 24. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 24 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 5.1Sample Problem 5.1 Solve Apply the concepts to this problem. • Use the aufbau diagram to place electrons in the orbital with the lowest energy (1s) first. • Continue placing electrons in each orbital with the next higher energy level. 2 1s 2s 2p 3p3s 4s
- 25. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 25 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Sample Problem 5.1Sample Problem 5.1 • The electron configuration of phosphorus is 1s2 2s2 2p6 3s2 3p3 . • The superscripts add up to the number of electrons. 2 Solve Apply the concepts to this problem. Write the electron configuration.
- 26. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 26 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Exceptional Electron Configurations Electron ConfigurationsElectron Configurations • You can obtain correct electron configurations for the elements up to vanadium (atomic number 23) by following the aufbau diagram for orbital filling.
- 27. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 27 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Exceptional Electron Configurations • You can obtain correct electron configurations for the elements up to vanadium (atomic number 23) by following the aufbau diagram for orbital filling. • If you were to continue in that fashion, however, you would assign chromium and copper the following incorrect configurations. Cr 1s2 2s2 2p6 3s2 3p6 3d4 4s2 Cu 1s2 2s2 2p6 3s2 3p6 3d9 4s2 Electron ConfigurationsElectron Configurations
- 28. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 28 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Exceptional Electron Configurations • The correct electron configurations are as follows: Cr 1s2 2s2 2p6 3s2 3p6 3d5 4s1 Cu 1s2 2s2 2p6 3s2 3p6 3d10 4s1 • These arrangements give chromium a half-filled d sublevel and copper a filled d sublevel. Electron ConfigurationsElectron Configurations
- 29. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 29 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Exceptional Electron Configurations Some actual electron configurations differ from those assigned using the aufbau principle because although half- filled sublevels are not as stable as filled sublevels, they are more stable than other configurations. Electron ConfigurationsElectron Configurations
- 30. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 30 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. What is the correct electron configuration of a sulfur atom? A. 1s2 2s2 2p4 3s2 3p6 B. 1s2 2s2 2p6 3s2 3p3 C. 1s2 2s2 2p6 3s2 3p4 D. 1s2 2s2 2p6 3s6 3p2
- 31. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 31 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. What is the correct electron configuration of a sulfur atom? A. 1s2 2s2 2p4 3s2 3p6 B. 1s2 2s2 2p6 3s2 3p3 C. 1s2 2s2 2p6 3s2 3p4 D. 1s2 2s2 2p6 3s6 3p2
- 32. 5.2 Electron Arrangement in Atoms >5.2 Electron Arrangement in Atoms > 32 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved. Key ConceptKey Concept Three rules—the aufbau principle, the Pauli exclusion principle, and Hund’s rule—tell you how to find the electron configurations of atoms.