CHEM 116 1st EditionExam # 2 Study Guide Chapter: 2 Tuesday Feb. 10EXAM 1Thursday Feb. 12Chapter 2 Atoms, Molecules, and Ions Nomenclature- Polyatomic Ions o Make index cards to memorize common ions Proton – positive charge, relative mass 1 amu(atomic mass unit)Neutron – neutral charge, relative mass 1 amuElectron – negative charge, relative mass 0- Protons and neutrons are located in the nucleus and determine nuclear properties of anatom - Electrons are located outside the nucleus in the “electron cloud” and determines the chemical properties - All atoms of the same element have the same number of protons - The number of protons is the Atomic Number (Z)- All atoms do not have to have the same number of neutrons o Atoms with the same number of protons and different numbers of neutrons are called isotopeso You can distinguish isotopes from one another by Nuclide Symbolo - The number of protons + the number of neutrons is called the Mass number (A)These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.- The weighted average atomic mass of an element is calculated by multiplying the atomicmass of each isotope of an element by the fractional abundance of the isotope o AM(WA) = AM(isotope 1) x FA(isotope1) + AM(isotope2) x FA(isotope2)… AM = atomic mass WA = weighted average FA = fractional abundance A Groups are the main groups or Representative Elements (predictable)1A – Alkali metals (form hydroxide in water)2A – Alkaline earth metals (form hydroxide in water)8A – Noble gases 7A – Halogens (salt former)6A – Chalcogens (rock/mineral formers)B Groups are Transition Metals (not predictable)Metalloids- an element that borders the stair step on the periodic table with the exception of Aluminum. Not a metal or nonmetal, but somewhere in between. Metals- to the left of the stair step on the periodic table with the exception of Hydrogen. Typically have high melting points. Nonmetals- to the right of the stair step on the periodic table along with Hydrogen. Tuesday Feb. 24Chemical formula- notation representing the relative proportions of atoms in a substanceExample. Aluminum oxide, Al2O3 2:3 ratio of aluminum to oxygenSodium chloride, NaCl 1:1 ratio of sodium to chlorineWater, H2O 2:1 ratio of hydrogen to oxygenSulfuric acid, H2SO4(aq) 2:1:4 ratio of hydrogen to sulfur to oxygenMolecular compounds - composed of identical molecules- A small definite grouping of atoms - Non-metals with non-metalso Ex. H2O, NH3Ionic compounds – composed of ions held together by electrostatic forces- A charged atom or molecule- Metals with non-metalso Ex. NaCl, Al2O3Elements can be:- Monatomic – He, Ne, and other noble gases- Diatomic – H2, O2, N2, and halogenso Homonuclear diatomic molecules – H2, Cl2o Heteronuclear – HCl, CO- Extended – metallic crystal structuresAllotropes – elements that exist in more than one form- Ex. Carbon: fullerene (C60), diamond, graphitePolymers – large molecular structures made of repeating unitsMonomers – the repeating unitNatural – wool, silkSynthetic – nylon, TeflonCation – positively charged ion (fewer electrons)Anion – negatively charged ion (more electrons)Monatomic Ion – single atom with a nonzero charge- Metals lose electrons (cations)- Nonmetals gain electrons (anions)Polyatomic Ion – molecule with a nonzero charge MEMORIZE THE LISTRule of Electrostatic Interactions (Coulombic forces) – opposites attract (between cation and anion)Ionic Compounds are neutral (charges are balanced)Formula Units – smallest group of atoms or ions represented by a chemical formula- Molecular compounds- molecule is smallest unito Ex. H2O, CO2- Ionic compounds – ionic formula is the smallest unit, contains the minimum # of ions to balance the charge, must be reducedo NaCl, Fe2(SO4)3o Example o a. Chromium (III) oxide is used as a green paint pigment. It is a compound composedofCr3+ andO2– ions. What is the formula of chromium (III) oxide? Cr3+ O2-Cr2O32(3) + 3(-2)=0=neutralo b. Strontium oxide is a compound composed of Sr2+ and O2– ions. Write the formula of this compound.Classify the following as either an ionic or molecular compound. CH4 - molecularBr2 - molecularCaCl2 - ionicKNO3 - ionicCH4O - molecularLiF – ionicOrganic Compounds – class of substances containing mostly carbon combined with other elements- living and nonliving- functional groupso Alcohol group OH is different from OH- and is set apart with a carbonMonatomic Ions- Metals form cations- Nonmetals form anions- Charges of cations can be determined based on the periodic table Groupo Group 1A = 1+o Group 2A = 2+o Group 3A = 3+o Under the stair step form the Group # and Group # - 2 Pb = 4+ or 2+Anions charges - Group 5A = 3-- Group 6A = 2-- Group 7A = -Zn2+ , Cd2+ , Ag+ can only have these charges- All other Transition metals have variable chargesNaming Rules for Ionic Compounds Cations with a unique charge, use element nameo Sodium ion, Na+ Cations with variable charge, use roman numeralso Iron(II) ion, Fe2+ Anions, use –ide suffixo Nitride, phosphide, arsenide, antimonideo Oxide, sulfideH+ is hydrogen ionH- is hydride ionPolyatomic Ions Anions, memorize table on blackboard, yes all of them Cations, memorize these 3o Ammonium ion, NH4+o Mercury(I) ion, Hg2+o Hydronium ion, H3O+Thursday Feb. 26Example. Naming an ionic compound from its formula Name the following: a. Mg3N2 – ionic (metal with nonmetal) – magnesium nitrideb. CrSO4 – ionic (metal with nonmetal) – chromium(II) sulfate a. CaO – calcium oxideb. PbCrO4 – lead(II) chromateExample. Writing the formula from the name of an ionic compound. Write formulas for the following compounds: a. iron(II) phosphate – Fe2+ and PO43- = Fe3 (PO4)2 b. titanium(IV) oxide – Ti4+ and O2- = Ti2 O4 = TiO2Be sure that you reduce your final answer.*Know the common ions, their formula, and their chargeNaming Molecular Compounds1. Do not reduce subscripts like you do in ionic2. Use Greek prefixes3. First species gets atom name4. Second gets –ide suffix5. Ao, oo reduce to just oExample. Naming a binary compound from its formula. Name the following compounds: a. N2O4 – dinitrogen tetroxideb. P4O6 – tetraphosphorous hexoxidec. Cl2O6 – dichlorine hexoxided. PCl3 – phosphorous trichloridee. PCl5 – phosphorous pentachloridef. disulfur dichloride – S2Cl2g. tetraphosphorous trisulfide