CHAPTER 7 CHEM II PERIODIC PROPERTIES OF ELEMENTS

PERIODIC TABLE GROUPS I.Periodic Table A.Nonmetals – upper right side of table, plus hydrogen B.Metalloids – elements along the zigzag line dividing metals and nonmetals C.Metals A.Alkali – group IA B.Alkaline Earth – Group IIA C.Transition metals – Group B D.Aluminum E.Post-transition – Ga, In, Tl, Sn, Pb, Bi, Po F.Lanthanides and Actinides (inner transition metals) – 2 rows beneath the main table

PROPERTIES OF METALS Properties of Metals Physical Properties: high electrical conductivity, high thermal conductivity, ductility, malleability, luster, most are white/silver (except gold and copper) Metallic bonding and the “electron sea” model: electrons between metal nuclei are not attached to any particular positive nucleus, but can wander from one to another Chemical Properties Tend to have low ionization energies and therefore form positive ions Compounds of metals and nonmetals tend to be ionic substances Most metal oxides are basic – those that dissolve in water react to form metal hydroxides React vigorously with acids

PROPERTIES OF NONMETALS Physical Properties Opposite of metals Most found in compound or diatomic form Most are gases (Br is a liquid and I is a solid) Chemical Properties Due to their high electron affinity, nonmetals gain electrons and form anions when they react with metals Compounds composed entirely of nonmetals are molecular substances (except salts of ammonium like NH 4 Cl) Most nonmetal oxides are acidic

PROPERTIES OF METALLOIDS Intermediate between metals and nonmetals More like nonmetals in chemical characteristics More like metals in some physical properties Solids at room temperature B, Si, Ge, As, Sb, Te, At

ANIONS AND CATIONS Most elements form ions that have a noble gas structure Anions (atoms that have gained electrons) S -2 charge, so 18 electrons = 1s 2 2s 2 2p 6 3s 2 3p 6 Cl -1 charge, so 18 electrons= 1s 2 2s 2 2p 6 3s 2 3p 6 Cations (atoms that have lost electrons) K +1 charge, so 18 electrons = 1s 2 2s 2 2p 6 3s 2 3p 6 Ca +2 charge, so 18 electrons= 1s 2 2s 2 2p 6 3s 2 3p 6 ** Isoelectronic species – ions or elements that have the same # of electrons**

TRANSITION METAL IONS These atoms lose valence electrons first They do not always attain a noble gas electron configuration Examples Iron: Fe 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 Fe +2 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 (lost 4s 2 electrons) Fe +3 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 (lost 4s 2 and 1 d electron) Gold: Au [Xe] 6s 1 4f 14 5d 10 Au + [Xe] 4f 14 5d 10 (lost 6s 1 electron) Au+2 [Xe] 4f 14 5d 9 (lost 6s 1 and 1 d electron)

GROUP TRENDS FOR MOST ACTIVE METALS Alkali Metals Physical Properties: low densities and melting points Chemical Properties: only exist in nature as compounds; increase in reactivity as you go down the table. Example Equations: alkali metals react with hydrogen gas 2 Na (s) + H 2(g) → 2 NaH (s) alkali metals react with water 2 Na (s) + 2 H 2 O (l) → 2 NaOH (s) alkali metals react differently with oxygen 4 Li (s) + O 2 (g) → 2 Li 2 O (s) lithium oxide 2 Na (s) + O 2(g) → Na 2 O 2(s) sodium peroxide K (s) + O 2(g) → KO 2(s) potassium superoxide

GROUP TRENDS FOR MOST ACTIVE METALS Alkaline Earth Metals Physical Properties: harder and denser than alkali metals Chemical properties: low first and second ionization energies but neither as low as alkali metals (not as reactive as alkali metals); increase in reactivity as you go down the table. Example Equations: 2 Mg (s) + 2 H 2 O (g) → 2 MgO (s) + H 2(g) 2 Ca (s) + 2 H 2 O (l) →2 Ca(OH) 2(s) + H 2(g)

GROUP TRENDS FOR SELECTED NONMETALS Hydrogen Physical Properties: lightest gas; physical properties similar to noble gases; abundant in Earth’s atmosphere and in living things Chemical properties: highly explosive gas; can form H+ ions or H- (hydride) ions Example Equations 2 H 2 (g) + O 2 (g) → 2 H­ 2 O H 2 (g) + 2 K (s) → 2 KH

Halogens (Group 17) Physical Properties/Uses (all are diatomic) Fluorine – most reactive& electronegative nonmetal, in toothpaste and Teflon Chlorine – a poisonous green gas used to kill bacteria Bromine – the only nonmetal that is liquid at room temp Iodine – solid at room temp, used in medicine Chemical properties: tend to gain one electron

Noble Gases (Group 18) Physical Properties/Uses: colorless, monoatomic gases Helium – used in balloons (low density) Neon – glows red-orange when electrons are excited Argon, krypton, xenon – used in various light bulbs Radon – radioactive element that is sometimes found in soil Chemical Properties Noble gases have full valence levels, therefore not reactive and do not form ions. Previously known as inert gases but a few compounds have been formed with Xe, and one with both Kr and Ar.