CH301 - chapter 6 notes

CH301 chapter 6 - 1 CH 301 Chapter 6 Chemical Periodicity 6-1 Periodic Table Noble gases ns2np6 8 electrons in highest energy level He Ne and Ar do

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1 CH 301 Chapter 6 Chemical Periodicity 6-1 Periodic Table Noble gases: ns 2 np 6 8 electrons in highest energy level He, Ne, and Ar do not form compounds Kr, and Xe will form compounds under extreme conditions Representative metals: All Group A elements the valence electrons will be in s for Group I A and Group II A the valence electrons will be in s and p for Group III A through Group VIII A valence electrons are located in the highest energy level for any element Although the Noble gases are generally included in the representative elements, not all chemistry authors agree with this categorization. As a rule, I accept the guidelines for representative elements as described in our text. Noble gases are included in the representative elements. Transition metals: Group B metals d-transition (or just transition) metals have electrons in the highest energy level of the s and d orbitals--ns (n-1) d orbitals. They do not have electrons in the p-orbitals. d-transition metals will generally remove electrons from the higher s-orbitals before removing electrons from the lower energy d-orbitals. f-transition (inner transition) metals add electrons to the f-orbitals f-transition metals are the Lanthamides and Actinides Periodic Properties of the Elements 6-2 Atomic Radii Atomic radii describes the relative sizes of atoms. atomic radii is determined by measurement of the distance between the nuclei of homonuclear molecules, e.g., Cl 2 Slide 4 p.236
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2 The atomic radii trend: Slide 7 p.238 Atomic radii increase within a column going from the top to the bottom of the periodic table. Atomic radii decrease within a row going from left to right on the periodic table. This last fact seems contrary to intuition. How does nature make the elements smaller even though the electron number is increasing? The reason the atomic radii decrease across a period is due to shielding or screening effect. ± Effective nuclear charge, Z eff , experienced by an electron is less than the actual nuclear charge, Z. ± The inner electrons block the nuclear charge’s effect on the outer electrons.
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This note was uploaded on 06/19/2008 for the course CH 301 taught by Professor Fakhreddine/lyon during the Spring '07 term at University of Texas at Austin.

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CH301 chapter 6 - 1 CH 301 Chapter 6 Chemical Periodicity 6-1 Periodic Table Noble gases ns2np6 8 electrons in highest energy level He Ne and Ar do

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