Unit 2:Elements and Compounds: Atoms, Molecules & Ions

CHM 1045: General Chemistry and Qualitative AnalysisDr. Jorge L. AlonsoMiami-Dade College Kendall CampusMiami, FLTextbook References: Modules #2 & 5

The Early Development of the Atomic Theory

Leucippus of Miletus & Democritus of Abdera (Gk. 5th Cent BC) More philosophical than experimental in origin. Matter is made up of very small individual atomos - objects that are indivisible. Everything is made up of these atoms, which move around in a void (a vacuum). The different physical properties -- color, taste, and so on -- of materials come about because atoms in them are different shapes and/or arrangements and orientations with respect to each other. Ancient Atomic Theory

Medieval Alchemy (, al-khimia) Science as an early form of investigation, with occult philosophical and spiritual traditions.

Jabir ibn Hayyan Merlin the Magician Principal aim of Alchemist: the transmutation of common metals into gold or silver. Cinnabar (red powder) Hg Zn, Cu, Fe Au or Ag the creation of a "panacea," or the elixir of life, a remedy that supposedly would cure all diseases and prolong life indefinitely.

Chemistry in the Age of Enlightment27 g 25 g + 2 g (s) (l) (g)(1743 - 1794){HgOMovie}Law of Conservation of Mass:

Law of Constant Composition (or Definite Proportions) (17541826)Compared masses of different elements within the same compound.In Water Ratio H :O1 : 8In H-Peroxide Ratio H : O1 :16*

Expt.Water Hydrogen +Oxygen#19.0 g 1.0 g8.0 g#218.0 g 2.0 g16.0 g#313.5 g 1.5 g12.0 g

Expt.Hydrogen Peroxide Hydrogen +Oxygen#117.0 g 1.0 g16.0 g#234.0 g 2.0 g32.0#325.5 g 1.5 g24.0 g

Daltons Law of Multiple ProportionWhen two elements form two different compounds, the mass ratio of the elements in one compound is related to the mass ratio in the other compound by a small whole number.C + O2 (high oxy.conc.) CO2

C + O2 (low oxy.conc.) CO

John Dalton (17661844).

Daltons Atomic Theory (1801)All matter is made up of small indivisible particles called atoms.The properties of the atoms of one element differ form those of all other elements.Atoms can neither be created nor destroyed.All atoms of the same element are identical in mass, size, and physical properties.Atoms combine in small whole number ratios to form compounds.All matter is made up of small indivisible particles called atoms.The properties of the atoms of one element differ from those of all other elements.Atoms can neither be created nor destroyed.All atoms of the same element are identical in mass, size, and physical properties.Atoms combine in small whole number ratios to form compounds.*

{Electroscope Movie}

The Electron Electrically charged particles can be rubbed-out of many substances such as glass rods, hair, shoes, rubber tires and shoes.Excess of electronsLack of electrons{Electroscope Movie*}Van de Graaff GeneratorElectric motorRubber bandRubber band rubs metals inside

The ElectronMovie 1Movie 2Movie 3cathode ray tubes produce negatively charged particles (electrons) from chemicals in batteries. J. J. Thompson is credited with their discovery (1897).Batteries (chemicals)Electron Rays

The Atom, circa 1900Plum pudding model, put forward by J. J. Thompson.

Positive sphere of matter with negative electrons imbedded in it.

Discovery of the NucleusIn 1909 Ernest Rutherford shot particles at a thin sheet of gold foil and observed the pattern of scatter of the particles.*

The Nuclear AtomSince some particles were deflected at large angles, J. J. Thompsons model could not be correct.{*Rutherfords Experiment}

The Nuclear AtomAccording to RutherfordHe postulated a very small, dense nucleus with the electrons around the outside of the atom.

Most of the volume of the atom is empty space.Difference of 105 = 100,000

Historical Development of Atomic Theory{Bohr Planetary vs. Quantum Model}

Scanning Tunneling Microscopy (STM)

Seeing Atoms: Scanning Tunneling Microscope

Seeing Atoms: Scanning Tunneling Microscope

Subatomic Particles: Charge & MassProtons and neutrons have essentially the same mass.The mass of an electron is so small we ignore it.Protons were discovered by Rutherford in 1919.

Neutrons were discovered by James Chadwick in 1932. {ProtonDiscoveryMovie}

ElementsPure substances that cannot be broken down into more elemental particles by ordinary chemical means.

IIIA IVA VA VIA VIIA

IA

IIB IVB VB VIB VIIB VIII IB IIBVIIIA

IIAA. Atomic number B. Mass number C. Isotopes D. Atomic mass or weigh

Elements & Atomic terminologyAtomic number (Z) = #p

Mass number (A) = (#p+) + (#no) A = Z + NIsotopes

Atomic mass or weigh (a.m.u. or grams)Atoms of the same element (same at. #), having different number of neutrons.The average mass of the isotopes of an element, considering their natural % abundance.#p = #e- in a neutral atomIdentifies the element

Atoms of the same element with different masses (mass number)IsotopesIsotopes have different numbers of neutrons.Isotopes of Carbon: (isotope notation)Mass number Atomic number 99.985% 0.015% 0% Natural Abundance0.000137% 99.999863% Natural Abundance7.59% 92.41% Natural AbundanceNatural Abundance: negligible 98.89% 1.11% negligible*(atomic number =1)(atomic number =2)(atomic number =3)Atomic mass or weigh?

Isotopes of Hydrogen1H2H3HNatural Abundance 99.985% 0.015% negligible unstable, radioactive

Isotopes of CarbonNatural Abundance 98.89% 1.11% negligible

12C13C14C

Table of Isotopes (partial)

Determination of Atomic MassMass spectrometer: can separate isotopes of an element based on their charge and mass, & measure their % abundance.Ionizing chamberSouth pole (-) of magnet attracts lighter isotope more easily than heavier isotope.

Mass SpectrometerMass Spectrum of Germanium (Ge)

Atomic Mass (Weight): the average mass of isotopes of an element, considering their natural abundanceIsotope % Abund. f.Abund. X Mass # = 3He 0.01 (0.0001 x 3) = 0.00034He 99.99 (0.9999 x 4) = +3.9996 4.00035Cl75.7737Cl24.23

24Mg78.9925Mg10.0026Mg11.01

Atomic Mass (Weigh): AM = (f1 x M#1) + (f2 x M#2) + *

2007 (B)#2Atomic Mass (Weigh): AM = (f1 x M#1) + (f2 x M#2) + 200?More exact

Properties of Metal, Nonmetals,and Metalloids

Organization or the Periodic Table: Groups (Families)The following four groups are known by their names:Transition MetalsRepresentative ElementsRepresentative Elements

Diatomic Molecules of ElementsThese seven + one elements occur naturally as molecules containing two atoms (diatomic).

In compounds they may combine in other ratios. NaCl, BaCl2, AlCl3,CCl4.At2Alonsos Rule of 7 + 1: Start with element #7, Nitrogen, trace a 7 and count 7 elements.Plus 1 more element, #1 Hydrogen

CompoundsPure substances (cannot be separated by physical means).Compounds can be broken down (decomposed) into more elemental particles (elements) by ordinary chemical means.H2O CO2 H2O2 CO CH4Molecular Formulas:Structural Formulas: (Space-filling )

Classification of CompoundsCovalent (Molecular) Compounds: Non-Metals + Non-Metals.Acids: Hydrogen + Nonmetals (polar covalent)Ionic Compounds Salts: Metal + Non-MetalBases: Metals + Hydroxide Ion (OH-)Acid Salts: Metal + Acid (Hydrogen + Nonmetal)

Organic Compounds: covalent compounds containing carbon (C) atom chains, with mostly H & O atoms attached to the chain.

Composed of a Non-Metal combined with another Non-Metal.Are mostly gases, liquids, and sometimes amorphous solids. Have low melting pointsBonded atoms share electrons.Covalent (Molecular) Compounds:H2O(s) *H2O(l) H2O(g)

Nomenclature: Molecular CompoundPrefix*- (name of 1st Element)Prefix- (root of 2nd Element) - IDE* Prefix mono- not used for 1st elementH2O CO2 H2O2 CO CH4Molecular Formulas:Structural Formulas: (Space-filling )

Ionic Compounds*

Ionic Compounds (Salts):Composed of a Metal ion (cation, M+) combined with an Non-Metal ion (anion, N-); atoms exchange transfer electrons.Are Crystalline Solids. Have high melting pointsSmallest component particle is called a formula unit, not a molecule.CationsAnions

(A) Ions with Fixed Charges (Oxidation Numbers)Zn2+Cd2+Ag1+Ionic Nomenclature: Binary SaltsName of 1st Element Root of 2nd Element -IDE1+2+3+3-2-1-Aluminum NitrideAluminum OxideAluminum BromideAl3+ N3- AlNAl3+ O2- Al2O3Al3+ Br- AlBr3

Ionic Nomenclature: Binary SaltsName of 1st Element (Roman Numeral) (or ous, -ic) Root of 2nd Element -IDE

(B) Ions with Variable Oxidation Numbers (Mostly Transition Metals)Iron (II) NitrideIron (III) NitrideFe2+ N3- Fe3N2Fe3+ N3- FeNTraditional Names:IUPAC Nomenclature:

Ionic Nomenclature: Binary SaltsIron (Ferrum): Fe 2+ (Iron II or Ferrous) Fe 3+ (Iron III or Ferric) Copper (Cuprum):Cu 1+ (Copper I or Cuprous) Cu 2+ (Copper II or Cupric)Mercury (Hydragyrum):Hg 1+ (Mercury I or Mercurous) Hg 2+ (Mercury II or Mercuric)(B) Ions with Variable Oxidation NumbersExceptions

Common Representative -ate Oxyanions

Ionic Nomenclature: Salts with Polyatomic IonsClO3 -chlorateNa+Na+Na+Na+

Common Polyatomic IonsNO3 -nitratePO4 3-phosphateAsO4 3-Arsenate

Common Representative -ate Oxyanions

Ionic Nomenclature: Salts with Polyatomic IonsName of 1st Element (Roman Numeral or ous, -ic) Name of Polyatomic ion (all end in -ATE)

IIIAIVAVAVIAVIIABO3 3-borateCO3 2-carbonateNO3 -nitrateOxygenSiO3 2-silicatePO4 3-phosphateSO4 2-sulfateClO3 -chlorateAsO4 3-arsenateSeO4 2-sellenateBrO3 -bromateTeO4 2-tellurateIO3 -iodate

Common Representative -ate OxyanionsPattern in # oxygens: Per-(oxyanion)-ate (oxyanion)-ate (oxyanion)- iteHypo-(oxyanion)-iteEvery step down the pattern ion has one less oxygen.Name of 1st Element (Roman Numeral or ous, -ic) Name of Polyatomic ion (Per- Hypo ATE ITE)

Polyatomic Ion MnemonicsClO3 -ClO2 -ClO -ClO4 -

IIIAIVAVAVIAVIIABO3 3-borateCO3 2-carbonateNO3 -nitrateOxygenSiO3 2-silicatePO4 3-phosphateSO4 2-sulfateClO3 -chlorateAsO4 3-arsenateSeO4 2-sellenateBrO3 -bromateTeO4 2-tellurateIO3 -iodate

Ionic Nomenclature: other Polyatomic Ions

NH4+ammonium

OH-hydroxideCN-cyanideSCN-thiocyanateC2H3O2-acetateMnO4-permanganateCrO42-chromateCr2O72-dichromateC2O42-oxalateO22-peroxide

Writing Ionic FormulasIf these subscripts are not in the lowest whole-number ratio, divide them by the greatest common factor.Mg2+OH-Mg 2+O2-Mg 2+PO43-Mg 2+SO32-

Mg3(PO4)2MgOH2Mg2O2MgSO3Mg(OH)2MgO

Given Chemical Names, determine Chemical FormulaCalcium Nitrate

Iron (III) Hydroxide

Zinc Phosphate

Copper (II) Oxide

Ca2+ NO3-Fe3+ OH-Zn2+ PO43-Cu2+ O2-Ca(NO3)2Fe(OH)3Zn3(PO4)2CuO

K2ONO2KMnO4Fe(OH)2Cu2OZn(NO3)2Cr2(SO3)5Given Chemical Formula, determine Chemical NamesPotassium OxideNitrogen DioxidePotassium PermanganateIron (II) HydroxideCopper (I) OxideZinc NitrateChromium (V) Sulfite

Name of Ionic Salt PREFIX- HydrateHydrates (Hydrated Salts)+ 2H2O Ionic substances containing water molecules incorporated into their crystalline structure release water upon heating, absorb water under cool, humid conditions+4 H2O- 2H2O- 4H2OAnhydrousHeat ()H2OH2OCu(NO3)2.5H2O

Acid NomenclatureDepends on the nomenclature ending of the anion that composes the acid.

-ide: hydro-(anion root) ic acidHCl -ate: (anion root) -ic acidHNO3 -ite: (anion root) -ous acidHNO2 Hydrochloric acidNitric acidNitrous acidAcid of Binary -IDEAcid of Polyatomic Ion:-ATE -ITE*

Acid NomenclatureBinary acid ends in -ide, add the prefix hydro- and change the ending to -ic acid HCl: hydrochloric acidHBr: hydrobromic acidHI: hydroiodic acidExercises:Acid of polyatomic ion ends in -ate, change ending to -ic acidHClO3: chloric acidHClO4: perchloric acidHCl, HClO3, HClO4 HBr,Acid of polyatomic ion ends in -ite, change the ending to -ous acidHClO2: chlorous acidHClO: hypochlorous acid

HI, HClO, HClO2Per-(oxyanion)-ate (oxyanion)-ate (oxyanion)- iteHypo-(oxyanion)-ite

Acidic Salts and Basic SaltsAcid Salts: salts of weak polyprotic acids. Are not necessarily acidic, but do neutralize bases.Basic Salts: salts of weak polyhydroxy bases. They do not dissolve well in water and thus exists mostly in the undissociated solid salt state instead of the dissolved basic state. They do neutralize acids.

Examples:AcidSaltHNO3NaNO3H2CO3Na2CO3H3PO4Na3PO4Solubility Rule:All OH- are insoluble except for IA metals, NH4+ & slightly soluble Ca 2+ Ba2+ & Sr2+ Mg(OH) 2(s)Fe(OH)3(s) Cr(OH) 3(s))(Milk of Magnesia)Acid Salt(s)-----------NaHCO3Na2HPO4NaH2PO4 sodium hydrogen carbonatesodium mono-hydrogen phosphate sodium di-hydrogen phosphate Cr3+ (aq) + 3 OH- (aq)solid salt dissolved (aq) base

Basic Organic Nomenclature: Alkanes and AlcoholsName # Carbons Structural FormulaMethane1CH4Ethane2CH3CH3Propane3CH3CH2CH3Butane4CH3CH2CH2CH3Pentane 5CH3CH2CH2CH2CH3Hexane 6 CH3CH2CH2CH2CH2CH3Heptane 7 CH3CH2CH2CH2CH2CH2CH3Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Organic Chemistry: deals with carbon compounds which form long chains of C atoms bonded to other C atoms.Alkanes: Carbon-hydrogen compounds with single bondsAlcohols: like alkanes, but with organic OH substituting one H.Methanol CH3OHEthanol CH3CH2OHPropanolButanolPentanolHexanolHeptanolOctanolNonanolDecanol

***Figure 2.4*Figure 2.9*Figure 2.10*Figure 2.11*Table 2.1******.******