Chemistry Week 2

Chemistry Week 2 - Unit # 1 1 (5) Periodic Table The...

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Unit # 1 1 -- Chemical Fundamentals -- (5) Periodic Table The periodic table systematizes our knowledge of the elements and their atoms. The table is divided into horizontal and vertical collections of atoms: Periods : horizontal rows; Groups : vertical columns; indicate elements with similar chemical properties, and often similar physical properties. Alkali metals, alkaline earth metals, halogens, noble gases, transition metals are important groups of elements to remember. Elements are generally classified according to their electrical conductivities: Periodic Table of the Elements Alkali Metals Alkaline-Earth Metals Transition Metals Chalcogens Halogens Noble Gases H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn Fr Ra Ac Rf Db Sg Bh Hs Mt 110 111 112 Lanthanides: Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Actinides: Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Metals “Metalloids” Semiconductors Nonmetals Molecules and Ions (1) Elemental Structures Do free atoms exist? At standard temperature and pressure (300 K and 1 atm), only He, Ne, Ar, Kr, Xe, Rn (the noble gases) are monatomic gases. Other elements exist as aggregates of atoms to form molecules (finite) or extended solids. Some examples: (a) Diatomic Molecules: hydrogen, nitrogen, oxygen, fluorine, chlorine (b) Triatomic Molecules: ozone (another allotrope of oxygen) (c) Rings: sulfur (d) Chains: selenium, tellurium
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Unit # 1 2 -- Chemical Fundamentals -- (e) Layers: carbon (graphite), phosphorus (red) (f) 3D Nets: carbon (diamond), boron, tin (g) 3D Sphere Packings: copper, sodium (2) Ions When atoms combine to form molecules or condensed phases (solids or liquids), they interact with each other via their electrons – remember, the electrons occupy most of the space of the atom. There are two typical ways that two atoms interact: (a) Sharing electrons – “covalent” interactions; (b) Transferring electrons – “ionic” interactions. When we look at the periodic table, there are three essential aspects to charge (electron) transfer between elements and their atoms under standard conditions of temperature and pressure (300 K, 1 atm.): (1) Noble gases (He, Ne, Ar, …) : are stable as isolated atoms and do not form compounds with other elements – no covalent nor ionic interactions. (EXCEPTIONS: Xe and Kr do form compounds with fluorine and oxygen, but these are very unusual examples. You will not be tested on this point.) (2) Metals (e.g., Na, Mg, Al, transition metals) : tend to lose electrons to nonmetallic elements; (3) Nonmetals (e.g., F, Cl, O, S, N) : tend to gain electrons from metals. An ion is a charged species formed from a neutral atom or molecule when electrons are gained or lost through some chemical change. Net charge = # protons # electrons.
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This note was uploaded on 03/27/2008 for the course CHEM 201 taught by Professor Miller during the Fall '07 term at Iowa State.

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Chemistry Week 2 - Unit # 1 1 (5) Periodic Table The...

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