Chapter 2Chapter 2Atoms, Molecules, Atoms, Molecules, and Ionsand Ions

Honors Chemistry 1Honors Chemistry 1

““We are each so atomically numerous and We are each so atomically numerous and so vigorously recycled at death that a so vigorously recycled at death that a significant number of our atoms – up to a significant number of our atoms – up to a billion for each of us, probably once billion for each of us, probably once belonged to Shakespeare. A billion more belonged to Shakespeare. A billion more each came from Buddha and Genghis each came from Buddha and Genghis Khan and Beethoven and …”Khan and Beethoven and …”

Bill BrysonBill Bryson

Cont.Cont.

Aristotle (Greek, 384-Aristotle (Greek, 384-322 B.C.) – did NOT 322 B.C.) – did NOT believe in atomsbelieve in atoms

NO experimentationNO experimentation

historyhistory

Democritus (Greek, 460-370 B.C.) – Democritus (Greek, 460-370 B.C.) – basic particle of matter basic particle of matter atomatom

NO experimentationNO experimentation

Cont.Cont.

John Dalton (English, John Dalton (English, 1803) – Dalton’s 1803) – Dalton’s Atomic TheoryAtomic Theory

Dalton’s Atomic TheoryDalton’s Atomic Theory

1.1. All matter composed of atomsAll matter composed of atoms2.2. Atoms of given element identical (e.g.size, Atoms of given element identical (e.g.size,

mass) – atoms of diff. elements differmass) – atoms of diff. elements differ3.3. Atoms can not be subdivided, created, or Atoms can not be subdivided, created, or

destroyeddestroyed4.4. Atoms of diff. elements combine in simple Atoms of diff. elements combine in simple

whole number ratios whole number ratios cmpds. cmpds.5.5. Atoms combine, separate, or rearrange in Atoms combine, separate, or rearrange in

chem. reactionschem. reactions # 2, 3 now revised# 2, 3 now revised

History reviewHistory review

Ancient cultures Ancient cultures present day present day Philosophy < > SciencePhilosophy < > Science Role of experimentationRole of experimentation What is a theoryWhat is a theory

Conservation of massConservation of mass

A + B A + B AB AB

1 mass unit + 3 mass units 1 mass unit + 3 mass units 4 mass units4 mass units

AB AB A + B A + B4 mass units 4 mass units 1 mass unit + 1 mass unit + 3 mass units3 mass units

Law of multiple Law of multiple proportionproportion

If 2 or more diff. cmpds. are composed of the If 2 or more diff. cmpds. are composed of the same 2 elements, the masses of 2same 2 elements, the masses of 2ndnd element element combined w/ a certain mass of the 1combined w/ a certain mass of the 1stst element element can be expressed as ratios of sm. whole can be expressed as ratios of sm. whole numbersnumbers

e.g. COe.g. CO 12 g C + 16 g O12 g C + 16 g O COCO22

12 g C + 32 g O 12 g C + 32 g O 16:32 = 1:216:32 = 1:2

Structure of the atomStructure of the atom

Atom – smallest particle Atom – smallest particle of an element that can of an element that can exist either alone or in exist either alone or in combination w/ other combination w/ other atomsatoms

STM imagesSTM images

Discovery of the electron Discovery of the electron (e(e--))

J.J. Thomson (1897)J.J. Thomson (1897)

Cathode ray tube (CRT)Cathode ray tube (CRT)

Thomson measured Thomson measured chg./ mass ratio of chg./ mass ratio of charged particlescharged particles

CRT (cathode ray tube)CRT (cathode ray tube)

The cathode ray tube (CRT), invented by The cathode ray tube (CRT), invented by German physicist Karl Ferdinand Braun in 1879, is an in 1879, is an evacuated glass envelope glass envelope containing an containing an electron gun (a source of (a source of electrons) and a electrons) and a fluorescent screen, screen, usually with internal or external means usually with internal or external means to accelerate and deflect the electrons. to accelerate and deflect the electrons. When electrons strike the fluorescent When electrons strike the fluorescent screen, light is emitted.screen, light is emitted.

Thomson (CRT)Thomson (CRT)

Electrons have a neg. (-) chgElectrons have a neg. (-) chg Have a very small massHave a very small mass

9.109 x 109.109 x 10-28-28 g = g =

(0.0000000000000000000000000009109 g)(0.0000000000000000000000000009109 g)

Discovery of atomic Discovery of atomic nucleusnucleus

Rutherford, Geiger, Rutherford, Geiger, Marsden (1908, Marsden (1908, 1909)1909)

Used (+) charged Used (+) charged particle beam aimed particle beam aimed at metal foilat metal foil

Gold foil experimentGold foil experiment

Possible results:Possible results:

Atoms have subatomic Atoms have subatomic particles, Ernest particles, Ernest Rutherford.Rutherford.

Students will be divided into two groups, atoms Students will be divided into two groups, atoms and alpha particles.and alpha particles.

““Atoms” will line up with their arms Atoms” will line up with their arms outstretched, touching only fingertips. outstretched, touching only fingertips.

““Alpha Particles” will first find a partner and Alpha Particles” will first find a partner and stand shoulder to shoulder.stand shoulder to shoulder.

Groups of “alpha particles” will line up behind Groups of “alpha particles” will line up behind one another. one another.

I will direct the “particles” to travel through the I will direct the “particles” to travel through the “atoms.” “atoms.”

Repeat with a second “layer” of atomsRepeat with a second “layer” of atoms

Rutherford: the nucleus Rutherford: the nucleus

(+) chg.(+) chg. Dense central core of atomDense central core of atom Contains nearly all mass of atomContains nearly all mass of atom

Atomic nucleusAtomic nucleus

2 types of particles:2 types of particles: Protons, (+) chg, Protons, (+) chg,

mass= 1.673x10mass= 1.673x10-24-24gg Neutrons, neutral chg, Neutrons, neutral chg,

mass= 1.675x10mass= 1.675x10-24-24gg

Discovery of the neutronDiscovery of the neutron

Chadwick, (1932), Chadwick, (1932), EnglandEngland

““Had the neutron been Had the neutron been isolated in the 1920s isolated in the 1920s (when work was started) (when work was started) it is very likely the atomic it is very likely the atomic bomb would have been bomb would have been developed in Europe, developed in Europe, undoubtedly by the undoubtedly by the Germans” Germans” Bill BrysonBill Bryson

symbolssymbols

Electron : Electron : ee--

Proton : Proton : pp++

Neutron : Neutron : nnoo

Isotopes of hydrogenIsotopes of hydrogen

Protium: 1 pProtium: 1 p++, 1 e, 1 e--

Deuterium: 1 pDeuterium: 1 p++, 1 e, 1 e--, 1 n, 1 n00

Tritium: 1 pTritium: 1 p++, 1 e, 1 e--, 2 n, 2 n00 (radioactive)(radioactive)

Atomic numberAtomic number

# of p# of p++ in nucleus in nucleus

Mass numberMass number

# of p# of p++ andand n n00 in nucleus in nucleus

IsotopesIsotopes

Different forms of the same element with Different forms of the same element with different massdifferent mass

Same # pSame # p++

Diff. # nDiff. # n00

Carbon Dating

Atomic #Atomic # Neutron #Neutron # mass# mass#

protiumprotium 11 00 11

deuteriumdeuterium 11 11 22

tritiumtritium 11 22 33

Isotopes of hydrogen

2 ways of writing 2 ways of writing isotopesisotopes(examples)(examples)

Carbon-12, uranium-235 ( the 12 & the Carbon-12, uranium-235 ( the 12 & the 235 are the mass numbers, e.g. U-235 235 are the mass numbers, e.g. U-235 has 92 phas 92 p++ and 143 n and 143 n00))

235 235 (235 is mass #, 92 is atomic #)(235 is mass #, 92 is atomic #)

9292UU

Relative atomic massRelative atomic mass

The mass of carbon-12 is exactly 12 The mass of carbon-12 is exactly 12 atomic mass units (u)atomic mass units (u)

This is a defined standardThis is a defined standard The mass of all other atoms are The mass of all other atoms are

expressed relative to carbon-12expressed relative to carbon-12

IsotopeIsotope Mass #Mass # Atomic massAtomic mass

Oxygen-16Oxygen-16 1616 15.99415.994

Copper-63Copper-63 6363 62.93962.939

Mass # v. Atomic mass

Avg. Atomic Mass (atomic Avg. Atomic Mass (atomic weight)weight)

WeightedWeighted avg. of atomic masses of avg. of atomic masses of naturally occurring isotopes of an naturally occurring isotopes of an elementelement

e.g. : naturally occurring e.g. : naturally occurring CuCu

69.17% Cu-63 (atomic mass 62.939)69.17% Cu-63 (atomic mass 62.939) 30.83% Cu-65 (atomic mass 64.927)30.83% Cu-65 (atomic mass 64.927) (0.6917)(62.939)+(0.3083)(64.927) = (0.6917)(62.939)+(0.3083)(64.927) =

63.54663.546Found on periodic tableFound on periodic table

The Periodic TableThe Periodic Table

5 minute history of 5 minute history of chemistrychemistry

Aristotle’s elementsAristotle’s elements

AirAir WaterWater FireFire EarthEarth

AlchemyAlchemy

Alchemy symbolsAlchemy symbols

Origin of modern element symbolsOrigin of modern element symbols(examples)(examples)

e.g. carbon, symbol C, from the Latin word e.g. carbon, symbol C, from the Latin word ""carbocarbo" meaning "" meaning "charcoalcharcoal" "

e.g. lead, symbol Pb, the origin of the symbol e.g. lead, symbol Pb, the origin of the symbol Pb is the Latin word "Pb is the Latin word "plumbumplumbum" "

e.g. mercury, symbol Hg, the origin of the e.g. mercury, symbol Hg, the origin of the symbol Hg is the Latin word "symbol Hg is the Latin word "hydrargyrumhydrargyrum" " meaning "meaning "liquid silverliquid silver""

e.g., Bismuth, symbol Bi, from the German e.g., Bismuth, symbol Bi, from the German word "word "bisemutumbisemutum" "

History (cont.)History (cont.)

Dmitri MendeleevDmitri Mendeleev His first periodic tableHis first periodic table

published in 1869published in 1869

Mendeleev’s periodic Mendeleev’s periodic tabletable

Left empty spaces for elements not yet Left empty spaces for elements not yet discovereddiscovered

When these were later discovered they When these were later discovered they ‘fit’ almost perfectly‘fit’ almost perfectly

e.g. scandiume.g. scandium

Modifications continue………Modifications continue………

Element symbolsElement symbols

One or two letter symbolsOne or two letter symbols First letter uppercase, e.g. Fe, CFirst letter uppercase, e.g. Fe, C Second letter (if present) lowercase, e.g. Second letter (if present) lowercase, e.g.

CaCa

Periodic tablePeriodic table

An arrangement of the elements in order An arrangement of the elements in order of their atomic numbers so that elements of their atomic numbers so that elements with similar properties fall in the same with similar properties fall in the same columncolumn

Groups: vertical Groups: vertical Periods: horizontalPeriods: horizontal

Alkali metals (group 1)Alkali metals (group 1)

Extremely reactiveExtremely reactive Not found as free elements in natureNot found as free elements in nature e.g. potassiume.g. potassium

Alkaline-Earth metals Alkaline-Earth metals (group 2)(group 2)

Reactive (not as reactive as grp 1)Reactive (not as reactive as grp 1) e.g. Mg, Cae.g. Mg, Ca

Transition elementsTransition elements(groups 3-12)(groups 3-12)

Metals, e.g. Cu, Ag, FeMetals, e.g. Cu, Ag, Fe Good conductorsGood conductors Less reactive that grps 1, 2Less reactive that grps 1, 2

Halogens (group 17)Halogens (group 17)

Most reactive nonmetals, e.g. Br, IMost reactive nonmetals, e.g. Br, I React w/ metals to form saltReact w/ metals to form saltss e.g. 2K + Cle.g. 2K + Cl22 2 KCl 2 KCl

Noble gases (grp 18)Noble gases (grp 18)

Non reactiveNon reactive e.g. Xe, Kre.g. Xe, Kr

TrendsTrends Electronegativity Electronegativity

Ability to attract electronsAbility to attract electrons

Atomic radius Atomic radius

Sub level blocks Sub level blocks

Monatomic ionsMonatomic ions

Ion with a single atomIon with a single atom e.g. Nae.g. Na++, Cl, Cl--

Polyatomic ionsPolyatomic ions

Ions w/ more than one atomIons w/ more than one atom e.g. SOe.g. SO44

2-2-, NO, NO33--

Ionic CompoundsIonic Compounds

NaNa++ + Cl + Cl-- NaCl NaCl MgMg2+2+ + Cl + Cl-- Cl Cl-- MgCl MgCl22 AlAl3+3+ Al Al3+3+ + O + O2-2- O O2-2- O O2-2- ? ?

Naming Ionic CompoundsNaming Ionic Compounds

NaClNaCl Sodium ChlorSodium Chlorideide Name of metallic ion first + root name of Name of metallic ion first + root name of

nonmetal + idenonmetal + ide

Metals that form more than Metals that form more than one ion use roman numerals one ion use roman numerals as part of the nameas part of the name

e.g. copper I Cue.g. copper I Cu++

copper II Cucopper II Cu2+2+

e.g. Cu(NOe.g. Cu(NO33))22 – copper II nitrate – copper II nitrate

Polyatomic ionsPolyatomic ions

e.g. ammonium ion NHe.g. ammonium ion NH44++

AlAl3+3+ & SO & SO442-2-

AlAl33++ Al Al33++ SO SO442-2- SO SO44

2-2- SO SO442-2-

AlAl22(SO(SO44))3 3 aluminum sulfatealuminum sulfate

PrefixesPrefixes

1 - mono1 - mono 2 – di2 – di 3 – tri3 – tri 4 – tetra4 – tetra 5 – penta5 – penta 6 – hexa6 – hexa 7 – hepta7 – hepta 8 – octa8 – octa

Molecular compoundsMolecular compounds(examples)(examples)

CClCCl44

carbon tetrachloridecarbon tetrachloride NN22OO33

dinitrogen trioxidedinitrogen trioxide

Acids Acids

Sulfuric HSulfuric H22SOSO44

Hydrochloric HClHydrochloric HCl Nitric HNONitric HNO33

Phosphoric HPhosphoric H33POPO44

Acetic HCAcetic HC22HH33OO22

Hydrofluoric HFHydrofluoric HF Carbonic HCarbonic H22COCO33

Diatomic moleculesDiatomic molecules

ClIF H BrONClIF H BrON ClCl22 II22

FF22

HH22

BrBr22

OO22

NN22

Formula mass, molar mass, Formula mass, molar mass, formula weight (F. W.)formula weight (F. W.)

E.g. CaClE.g. CaCl22 1 Ca atom x 40.078u / Ca atom = 40.078u1 Ca atom x 40.078u / Ca atom = 40.078u

2 Cl atoms x 35.453u / Cl atom = 70.906u2 Cl atoms x 35.453u / Cl atom = 70.906u

+ ________+ ________

formula mass CaClformula mass CaCl22 = 110.984u = 110.984u