CHAPTER 9 - Department of Department of 1 Chemistry...

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Unformatted text preview: Department of Department of 1 Chemistry Chemistry CHEM 1A03: Intro. Chemistry I Essential Elements: Chemistry, Life & Health Ch.9: The Periodic Table and Some Atomic Properties Department of Department of 2 Chemistry Chemistry Noble gases, Group 18 (8A) • n s 2 n p 6 stable electron configurations • Other elements try to attain these configurations • Considered chemically “inert” until 1962 – many noble gas compounds known, including e.g. KrF 2 , XeF 2 , XeF 4 , XeF 6 XeO 3 , XeOF 2 # , XeOF 4 , XeO 2 F 4 Much of this research based at McMaster ! # Brock, D. S., et al. , J. Am. Chem. Soc. , 129 , 2007, 3598-3611. p. 365 (344, 9 th ed.) © Department of Department of 3 Chemistry Chemistry Non-metals • Main group (s and p block) non-metals tend to gain electrons p. 366 (345, 9 TH ed.) © Department of Department of 4 Chemistry Chemistry Example: Descriptive Halogen Chemistry 1) Ability to oxidize increases up the group (towards F). For example: YES: Cl 2 (g) + 2 I − (aq) → I 2 (aq) + 2 Cl − (aq) NO: Br 2 (l) + Cl − (aq) → no rxn 2)They react with metals to form salts! e.g. NaCl 2 Na(s) + Cl 2 (g) → 2 NaCl(s) Fig. 9-16 (9-15, 9 th ed.) Fig. 9-17 (9-16, 9 th ed.) p. 384 (362, 9 th ed.) © Department of Department of 5 Chemistry Chemistry Example: Descriptive Halogens Chemistry 3) Halogen mp/bp increases down group 17A (more on this in Ch 12) Cl 2 (g), Br 2 (l), I 2 (s) Fig. 9-13 (9-12, 9th ed.) p. 382 (360, 9 th ed.) © Department of Department of 6 Chemistry Chemistry Metals • Main group (s and p block) metals (and H) tend to lose electrons p. 365 (344, 9 th ed.) © Department of Department of 7 Chemistry Chemistry Example: Group 1 and 2 metals • Alkali metals (Group 1) oxidize more readily than alkaline earth metals (Group 2) • Both oxidize easily in water [Fig. 9-15 (9-14, 9 th ed.)] K Ca, with added phenolphthalein Make sure you can write these reactions! p. 384 (361, 9 th ed.) © Department of Department of 8 Chemistry Chemistry General trends in physical properties Across a period: – Metallic properties decrease – melting point (mp) varies with t ype of bonding: Metals (Na, Mg, Al) Fig. 9-14 (9-13, 9 th ed.) p. 382 (360, 9 th ed.) Non-metals (P, S, Cl molecules, and Ar, atoms) Metalloid (Si, network solid) © Department of Department of 9 Chemistry Chemistry A key idea for periodic trends: Screening • Outer e − of an atom are screened by the core e − from feeling the full attractive charge (Z) from the nucleus • Outer e − feel an effective nuclear charge, Z effective • Simply, , where S = # core e − • In reality, s, p and d e − are screened to different extents; outer e − also screen each other [note: omit eq. 9.5] S Z Z eff − = p. 368 (348, 9 th ed.) © Department of Department of 10 10 Chemistry Chemistry Atomic radius (Fig. 9-4) p. 367-371 (347-350, 9 th ed.) © Department of Department of 11 11 Chemistry Chemistry Atomic radius – general trends • Decreases across a period – Z increases, and e...
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