TroChapter8Notes.docx - Tro’s Chemistry Chapter 8 – Periodic Properties of the Elements Page 1 of 8 Acknowledgements Some of the images are adopted

TroChapter8Notes.docx - Tro’s Chemistry Chapter 8 –...

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Tro’s Chemistry Chapter 8 – Periodic Properties of the Elements Page 1 of 8 Acknowledgements: Some of the images are adopted from Tro’s textbook to aid student learning. Key skills: Writing electron configurations and orbital diagrams of atoms and ions, difference between valence electrons and core electrons, electron configuration from the periodic table, using periodic trend to predict atomic size, ionic size, relative ionization energy, and metallic characters, writing reactions for alkali metals and halogens. Review questions: 1, 4, 7, 9, 11-21, 23-40. Suggested problems: 41-43, 51, 59, 61, 63, 65, 67, 69, 71, 73, 75, 81, 83. 8.2 The Development of the Periodic Table Elements known to human (refer to chapter 2, p61 accounts for 111 of them) as follows: Before 1800: only 38 1800 – 1849: 22 1850 – 1899 (Mendeleev): 25 1900 – 1949: 11 1950 – 1999: 15 2000 – date: 7 Attempts to organize the elements in some pattern: Dobereiner (1780-1849) – Triads Newlands (1837-1898) – Octaves Mendeleev (1834-1907), Meyer (1830-1895) – modern periodic table o Elements are arranged in rows from left to right in increasing order of mass in such a way that the columns contained elements with similar properties. o Bold moves : 1. Existence of undiscovered elements 2. Placing iodine after tellurium Moseley (1887-1915) – used atomic number instead of atomic weight 8.3 Electron Configurations: How Electrons Occupy Orbitals Chemical reactions happen as a result of exchange or sharing of outer electrons of participating atoms. Electron configuration classifies the electrons in different layers according to quantum theory. Two new terms need to be considered: electron spin and sublevel energy splitting. Electron Spin and the Pauli Exclusion Principle Electrons have electromagnetic properties. They generate electromagnetic field. An orbital can contain a maximum of two electrons. These two electrons spin in two different directions in the electron cloud (orbital), spin up (or ↑) and spin down (or ↓). This results in increased attractive force and stability in the atomic system.
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