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Periodic Properties and the Elements

Periodic Properties and the Elements. Sections 7.1-7.3. Objectives. Examine the history of the periodic table Identify atomic properties that depend on the attraction between electrons and nuclei Examine periodic trends. Valence orbitals Effective nuclear charge. Bonding atomic radius

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Periodic Properties and the Elements

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  1. Periodic Properties and the Elements Sections 7.1-7.3

  2. Objectives • Examine the history of the periodic table • Identify atomic properties that depend on the attraction between electrons and nuclei • Examine periodic trends

  3. Valence orbitals Effective nuclear charge Bonding atomic radius Isoelectronic series Key Terms

  4. Development of Periodic Table • Elements in the same group have similar chemical properties • not identical

  5. Development of Periodic Table Dmitri Mendeleev and Lothar Meyer independently came to the same conclusion about how elements should be grouped

  6. Development of Periodic Table Ex: Mendeleev predicted the discovery of germanium (which he called eka-silicon) as an element with an atomic weight between that of zinc and arsenic, but with chemical properties similar to those of silicon

  7. Periodic Trends • In this chapter, we will rationalize observed trends in • Sizes of atoms and ions • Ionization energy • Electron affinity

  8. Effective Nuclear Charge • Electrons are both attracted to the nucleus and repelled by other electrons • The nuclear charge that an electron experiences depends on both factors

  9. Effective Nuclear Charge The effective nuclear charge, Zeff, is found this way: Zeff = Z − S where Z is the atomic number and S is a screening constant, usually close to the number of inner electrons

  10. Sizes of Atoms Atomic radius= 1/2 of the distance between covalently bonded nuclei

  11. Sizes of Atoms Bonding atomic radius tends to… …decrease from left to right across a row due to increasing Zeff. …increase from top to bottom of a column due to increasing value of n

  12. Periodic Trends: Atomic Radius DECREASES I N C R E A S E S

  13. Sizes of Ions • Ionic size depends upon: • Nuclear charge • Number of electrons • Orbitals in which electrons reside

  14. Sizes of Ions • Cations are smaller than their parent atoms • The outermost electron is removed and repulsions are reduced

  15. Sizes of Ions • Anions are larger than their parent atoms • Electrons are added and repulsions are increased

  16. Sizes of Ions • Ions increase in size as you go down a column • Due to increasing value of n

  17. Sizes of Ions • In an isoelectronic series, ions have the same number of electrons. • Ionic size decreases with an increasing nuclear charge.

  18. Homework • 7.13 and 7.14 page 292 • 7.23, 7.24, and 7.26; 7.29 and 7.30 page 293

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