Chem 154 - 2012 Winter - handout 08

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Unformatted text preview: 7 227 90 90 232.04 232.04 91 91 231.04 231.04 92 92 238.03 238.03 93 93 237 237 94 94 244 244 95 95 243 243 96 96 247 247 97 97 247 247 98 98 251 251 99 99 252 252 100 100 257 257 101 101 258 258 102 102 259 259 103 103 262 262 Ac Th Th Pa Pa U U Np Np Pu Pu Am Am Cm Cm Bk Bk Cf Cf Es Es Fm Fm Md Md No No Lr Lr Actinium Actinium Thorium Thorium Protactinium Protactinium Uranium Uranium Neptunium Neptunium Plutonium Plutonium Americium Americium Curium Curium Berkelium Berkelium Californium Californium Einsteinium Einsteinium Fermium Fermium Mendelevium Mendelevium Nobelium Nobelium Lawrencium Lawrencium Name Metals and Nonmetals NOTE: Most elements are metals, which is reflected in the colour scheme of the P.T. Metals are shown in blue, non-metals in green and the metalloids in a diagonal line in between in yellow. Noble Gases • The group 18 elements are called noble gases. • They always have a completely occupied outer shell, which is a particularly stable configuration. • It is difficult to remove or add an electron. ⇒ Because of this, these gases are not at all reactive; they are inert. • Noble gases are odourless, colourless and monatomic. • They have very low boiling and melting points EXAMPLE: Krypton http://www.periodicvideos.com/videos/036.htm • Noble gases have many applications: x He is used to cool superconducting magnets used in NMR and MRI y He has replaced hydrogen in blimps and balloons z Providing a protective atmosphere (packaging, welding,. . . ) { Lighting e.g. neon lamps, halogen lamps (Krypton with iodine or bromine) 2–72 EXAMPLE: Xenon has a nearly continuous spectrum ⇒ used for film projectors. 15,000-watt xenon short-arc lamp used in IMAX projectors http: //en.wikipedia.org/wiki/File:Xenon_short_arc_1.jpg NOTE: An ion is an atom which has more or less electrons than protons. • Starting from a neutral atom, if we x remove an electron ⇒ positive charge (cation) y add an additional electron ⇒ negative charge (anion). NOTE: Electrical current occurs when ions are transported. NOTE: Elements either side of group 18 tend to adopt noble gas-like stable configurations relatively easily. • They are also very reactive, see for example • Na http://www.periodicvideos.com/videos/011.htm or • Fl http://www.periodicvideos.com/videos/009.htm. x Lose electrons to become positive ions. ⇒ This happens to the s-block elements (main group metal ions). • Examples include K + , Ca2+ NOTE: Aluminium also does this: Al 3+ . y Gain electrons (p-block elements) to become negative ions ⇒ This happens in the 16 and 17 groups • Examples include Cl − , S−2 . NOTE: ions with charge of −3 do exist, but are rare. NOTE: Some of these ions play an important rôle in biochemistry. EXAMPLE: The Calcium ion Ca2+ is required for many biological processes (signal transduction) including • neuron firing via the synapse. Neurons are cells that process information in the nervous system of the body. • Blood clotting • Muscle contraction • See the Calcium video http://www.periodicvideos.com/videos/020.htm...
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