Inorganic Lecture 2

Inorganic Lecture 2 - Lecture 2 Continuing atomic structure...

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1 Lecture 2 • Continuing atomic structure • Periodic Trends • Concepts based on electrons • Chapter 1 sections 10 and 15 Penetration and Shielding • We can gain useful info by considering the different screening effects that electrons have on one another • For example, it helps explain electronic configurations • As electrons get further from the nucleus the energy differences between orbitals with the same value of n gets smaller and it becomes harder to predict these effects
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2 Penetration •Radial distribution functions allows us to envision the region in space in which the electron is found •They show us that the 2s and 2p atomic orbitals penetrate the 1s •The 2s atomic orbital is more penetrating than the 2p Shielding • Electrons that are further from the nucleus are shielded from the charge of the nucleus by electrons that are closer to the nucleus • The charge that an electron actually “feels” is the effective nuclear charge Z eff • An electron in a 2s or 2p atomic orbital experiences the effective charge, Z eff , of a nucleus partly shielded by the 1s electrons
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3 Z* = Z - S • Z* = effective nuclear charge • Z = atomic number (the actual charge of the nucleus, # of protons) • S = screening constant • Z* < Z • Z* can be calculated using Slater’s Rules Slater’s Rules If the e - in question resides in an ns- or np-orbital • Write out the electron configuration of the element in the following order and groupings: (1s), (2s, 2p), (3s, 3p), (3d), (4s, 4p), (4d), (5s, 5p) etc… • All e - s in shells higher than the e - in question contribute zero to S • Each e - in the (ns, np) group contributes 0.35 to S • Each e - in the (n-1) shell contributes 0.85 to S • Each e - in the (n-2) shell or lower shells contributes 1 to S
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4 10 Ne 9 F 8 O 7 N 6 C 5 B 4 Be 3 Li 2 2 He 1 H 1 Z* S Z element n Slater’s Rules If the e - in question resides in an nd- or nf-orbital • Write out the electron configuration of the element in the following order and groupings: (1s), (2s, 2p), (3s, 3p), (3d), (4s, 4p), (4d), (5s, 5p) etc… • All e - s in shells higher than the e - in question contribute zero to S • Each e - in the (nd, nf) group contributes 0.35 to S • Each e - in a lower group than the one being considered contributes 1 to S
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5 Let’s Practice Calculating Z*
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This note was uploaded on 04/07/2008 for the course CHEM 311 taught by Professor Aitken during the Spring '08 term at Duquesne.

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Inorganic Lecture 2 - Lecture 2 Continuing atomic structure...

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