Atoms, Molecules, Atoms, Molecules, and Ionsand Ions

Chapter 2Chapter 2

DemocritusDemocritus

460 BC460 BC First to propose First to propose

atomic nature of atomic nature of mattermatter

““atomos” - atomos” - indivisibleindivisible

DaltonDalton

Studied Studied experiments experiments from other from other scientistsscientists

Law of multiple Law of multiple proportionsproportions

First Modern First Modern Atomic TheoryAtomic Theory

Dalton’s PostulatesDalton’s Postulates

Each element is composed of tiny Each element is composed of tiny particlesparticles

All atoms of an element are identicalAll atoms of an element are identical Atoms of an element are not Atoms of an element are not

changed into different types of changed into different types of atoms in a chem rxnatoms in a chem rxn

Compounds form when 2 or more Compounds form when 2 or more atoms combineatoms combine

J.J. ThomsonJ.J. Thomson

Cathode ray expeCathode ray experimentsriments

Discovered Discovered electrons and electrons and their charge-to-their charge-to-mass ratiomass ratio

Plum Pudding Plum Pudding Model of AtomModel of Atom

Plum Pudding ModelPlum Pudding Model

JJ ThomsonJJ Thomson 18971897 Electrons float in Electrons float in

a positively a positively charged ooze.charged ooze.

No nucleusNo nucleus

electrons

Positively charged ooze

MillikanMillikan

Oil drop experimOil drop experimentent

Determined the Determined the charge of the charge of the electron as -1electron as -1

RutherfordRutherford

1911 - Gold foil exp1911 - Gold foil experimenteriment

Discovered that the Discovered that the atom was mostly atom was mostly empty space with a empty space with a small dense small dense positively charged positively charged core he called the core he called the nucleusnucleus

Also discovered Also discovered protons in 1919protons in 1919

The Nuclear ModelThe Nuclear Model

19111911 RutherfordRutherford *Nucleus: *Nucleus:

positively positively charged centercharged center

Electrons orbit Electrons orbit the nucleusthe nucleus

*Atom is mostly *Atom is mostly empty space.empty space.

ChadwickChadwick

Discovered neutrDiscovered neutron in 1932on in 1932

Neutrons are Neutrons are about the same about the same size as a proton, size as a proton, but have no but have no charge.charge.

Found in nucleusFound in nucleus

BohrBohr

Planetary model Planetary model of atom in 1913of atom in 1913

Wavelengths of Wavelengths of emissions of emissions of hydrogen hydrogen spectrumspectrum

Bohr’s ModelBohr’s Model

19131913 Electrons orbit the Electrons orbit the

nucleus in specific nucleus in specific energy levelsenergy levels

Electrons can jump Electrons can jump between energy between energy levelslevels

Each energy level Each energy level holds a specific holds a specific number of electronsnumber of electrons

nucleus

Energy levels

n=1

n=2

Electron cloud modelElectron cloud model SchrodingerSchrodinger 19261926 We now know that We now know that

electrons move electrons move very fast around very fast around the nucleus.the nucleus.

This fast movement This fast movement causes the causes the electrons to form a electrons to form a “cloud” around the “cloud” around the nucleus.nucleus.

The cloud is a The cloud is a mathematical mathematical probability of where probability of where the electrons are in the electrons are in orbit.orbit.

Marie CurieMarie Curie

RadiationRadiation Discovered Discovered

radium and radium and poloniumpolonium

Used X-ray Used X-ray machines in WWImachines in WWI

BecquerelBecquerel

Discovered Discovered radiationradiation

Worked with Worked with CuriesCuries

Discovery of Atomic Discovery of Atomic StructureStructure

What is it?What is it? characteristicscharacteristics

Alpha Alpha particles particles ((αα))

Helium nucleus Helium nucleus ((44He)He)

2 protons, 2 2 protons, 2 neutrons, positive neutrons, positive chargecharge

WeakestWeakest

Beta Beta particles particles ((ββ))

High speed eHigh speed e-- emitted from emitted from nucleus at time nucleus at time of creationof creation

-1 charge-1 charge

Weak Weak

Gamma Gamma particles particles ((γγ))

High energy X-High energy X-rayray

StrongestStrongest

Cause and cure Cause and cure cancercancer

Modern View of Atomic Modern View of Atomic StructureStructure

ProtonProtonss

NeutronNeutronss

Electrons Electrons

LocatioLocationn

NucleuNucleuss

NucleusNucleus Moving very fast in Moving very fast in energy levels around energy levels around nucleusnucleus

RelativRelative sizee size

LargeLarge LargeLarge Extremely tinyExtremely tiny

ChargeCharge +1+1 00 -1-1

Symbol Symbol pp+ + nn00 ee--

Atomic Mass - based on #s of Atomic Mass - based on #s of protons, neutrons, and electrons in protons, neutrons, and electrons in the atomthe atom

protons and neutrons have about protons and neutrons have about thethesame mass and size; found in thesame mass and size; found in thenucleus; make up almost ALL of thenucleus; make up almost ALL of themass of the atommass of the atom

electrons are extremely tiny, haveelectrons are extremely tiny, havealmost NO massalmost NO mass

on periodic table, atomic mass ison periodic table, atomic mass isAVERAGE atomic massAVERAGE atomic mass

IsotopesIsotopes

isotopes - atoms of an isotopes - atoms of an element that have different element that have different massesmasses

same # of p+, differentsame # of p+, different# of n# of n

Some symbols, Some symbols, formulas, and termsformulas, and terms A = mass number = protons + A = mass number = protons +

neutronsneutrons Z = atomic number = protons Z = atomic number = protons

= electron (neutral atom)= electron (neutral atom) number of neutrons = mass # number of neutrons = mass #

- protons = A-Z- protons = A-Z

Isotopic notationIsotopic notation

Element-AElement-A AAXX X-AX-A

Neon - 20Neon - 20 2020NeNe Ne-20Ne-20

Cobalt - 60Cobalt - 60 6060CoCo Co-60Co-60

Average Atomic MassAverage Atomic Mass

Average of all the isotopes found Average of all the isotopes found in naturein nature

Naturally occurring chlorine is Naturally occurring chlorine is 75.78% 75.78% 3535Cl, which has an atomic Cl, which has an atomic mass of 34.969amu and 24.22% mass of 34.969amu and 24.22% 3737Cl, which has a mass of 36.966 Cl, which has a mass of 36.966 amu. Calculate the average amu. Calculate the average atomic mass.atomic mass.

Practice problem on page 46.Practice problem on page 46.

DevelopmentDevelopment

DobereinerDobereiner– Triads – groups of 3 based on similar Triads – groups of 3 based on similar

propertiesproperties NewlandsNewlands

– Law of octaves – same properties Law of octaves – same properties repeat every 8repeat every 8thth element element

– 7 rows of 7 elements each7 rows of 7 elements each

MendeleevMendeleev

Father of the Periodic TableFather of the Periodic Table Elements were put into columns Elements were put into columns

according to properties and according to properties and increasing atomic mass.increasing atomic mass.

Rows varied in length.Rows varied in length. LEFT BLANK SPOTS FOR LEFT BLANK SPOTS FOR

UNDISCOVERED ELEMENTS.UNDISCOVERED ELEMENTS. Properties of the elements Properties of the elements

depends on atomic mass.depends on atomic mass.

MoseleyMoseley

Used X-rays to study protons in Used X-rays to study protons in the atomsthe atoms

He noticed that atomic number He noticed that atomic number increased according to increased according to Mendeleev’s chart.Mendeleev’s chart.

Led to modern periodic lawLed to modern periodic law

Periodic Law, based on Periodic Law, based on Moseley’s WorkMoseley’s Work

The properties of the elements The properties of the elements are a periodic function of their are a periodic function of their atomic number.atomic number.

That is, the properties of the That is, the properties of the elements depends on the atomic elements depends on the atomic #.#.

OrganizationOrganization

MendeleevMendeleev Elements are arranged according to Elements are arranged according to

their properties.their properties. Each group or family (vertical columns) Each group or family (vertical columns)

have similar properties.have similar properties. Each horizontal row is called a period.Each horizontal row is called a period. The A groups (columns 1,2,13-18) are The A groups (columns 1,2,13-18) are

representative elements.representative elements. The B groups (columns 3-12) are The B groups (columns 3-12) are

transition elements.transition elements.

Family NamesFamily Names

Group IA (1) – Alkali MetalsGroup IA (1) – Alkali Metals Group IIA (2) – Alkaline Earth MetalsGroup IIA (2) – Alkaline Earth Metals Group VIA (16) – ChalcogensGroup VIA (16) – Chalcogens Group VIIA (17) – HalogensGroup VIIA (17) – Halogens Group VIIIA (18) – Noble GasesGroup VIIIA (18) – Noble Gases Groups 3-12 – Transition MetalsGroups 3-12 – Transition Metals Top Row – LanthanidesTop Row – Lanthanides Bottom Row - ActinidesBottom Row - Actinides

Valence ElectronsValence Electrons

Electrons in the outermost energy Electrons in the outermost energy level of the atom.level of the atom.

Electrons most responsible for Electrons most responsible for atom behavior.atom behavior.

Valence ElectronsValence Electrons

Alkali Metals – 1Alkali Metals – 1 Alkaline Earth Metals – 2Alkaline Earth Metals – 2 Boron Group (13) – 3Boron Group (13) – 3 Carbon Group (14) – 4Carbon Group (14) – 4 Nitrogen Group (15) – 5Nitrogen Group (15) – 5 Chalcogens – 6Chalcogens – 6 Halogens – 7Halogens – 7 Noble Gases - 8Noble Gases - 8

StabilityStability

Ultimate goal: to become stableUltimate goal: to become stable Octet rule: 8 valence electrons make an Octet rule: 8 valence electrons make an

atom stable because that completes the atom stable because that completes the outer energy level; full = stableouter energy level; full = stable

Atoms want to achieve a noble gas Atoms want to achieve a noble gas electron configuration – isoelectronic.electron configuration – isoelectronic.

Some exceptions: a full or half-full Some exceptions: a full or half-full sublevel will also make an atom sublevel will also make an atom relatively stablerelatively stable

Properties of MetalsProperties of Metals

Good conductors of heat & Good conductors of heat & electricityelectricity

Malleable (pounded into sheets)Malleable (pounded into sheets) Ductile (stretched into wires)Ductile (stretched into wires) Hard, shiny appearanceHard, shiny appearance 3 or less valence electrons 3 or less valence electrons Lose electrons to form compoundsLose electrons to form compounds Left side of PTLeft side of PT

Properties of Properties of NonmetalsNonmetals Poor conductors of heat & electricityPoor conductors of heat & electricity Good insulatorsGood insulators Solids are dull and brittle.Solids are dull and brittle. Most are gases at room Most are gases at room

temperature.temperature. 5 or more valence electrons5 or more valence electrons Gain electrons to form compoundsGain electrons to form compounds Right side of PTRight side of PT

Properties of Properties of MetalloidsMetalloids SemiconductorsSemiconductors Share electrons to form Share electrons to form

compoundscompounds Both metallic and nonmetallic Both metallic and nonmetallic

propertiesproperties Follow stair-step lineFollow stair-step line

Molecules - Molecules - Two or more Two or more atoms tightly bound atoms tightly bound togethertogether Chemical formulasChemical formulas

– HH22OO

– CaCa33(PO(PO44))22

Diatomic moleculesDiatomic molecules– BrBr22II22NN22ClCl22HH22OO22FF22

Molecular compoundsMolecular compounds– Composed of molecules and contain Composed of molecules and contain

more than one type of atommore than one type of atom Most contain only nonmetalsMost contain only nonmetals

Molecular formulaMolecular formula– Actual numbers and types of atomsActual numbers and types of atoms– HH22O; CO; C66HH66

Empirical formulaEmpirical formula– Only gives the ratio of atomsOnly gives the ratio of atoms– HH22O; CHO; CH

Structural formulaStructural formula– Shows how atoms are bondedShows how atoms are bonded

Ions and Ionic Ions and Ionic CompoundsCompounds Ion – charged particleIon – charged particle Cation – positive ionCation – positive ion Anion – negative ionAnion – negative ion Polyatomic ions – atoms joined in Polyatomic ions – atoms joined in

a molecule, but with an overall a molecule, but with an overall chargecharge

Charges (Oxidation Charges (Oxidation numbers)numbers) Pattern on PTPattern on PT Transition metals varyTransition metals vary

– Can be determined from formulaCan be determined from formula CuClCuCl22

– Are denoted with roman numeralsAre denoted with roman numerals Iron (III) nitrateIron (III) nitrate

Writing FormulasWriting Formulas

MUST HAVE CHARGES TO WRITE MUST HAVE CHARGES TO WRITE FORMULAS!!!FORMULAS!!!

Sodium chlorideSodium chloride Barium bromideBarium bromide Copper (II) sulfateCopper (II) sulfate Iron (III) nitrateIron (III) nitrate Magnesium phosphateMagnesium phosphate

Binary CompoundsBinary Compounds

Metal-nonmetal compound Metal-nonmetal compound consisting of 2 elementsconsisting of 2 elements– Name the cation.Name the cation.– Name the anion by changing the Name the anion by changing the

ending to –ide.ending to –ide. Example: NaCl – sodium chlorExample: NaCl – sodium chlorideide Example: LiExample: Li22S – lithium sulfS – lithium sulfideide

Naming Compounds Naming Compounds Containing Polyatomic Containing Polyatomic IonsIons 1. Name the cation.1. Name the cation. 2. Name the anion. Do NOT change the 2. Name the anion. Do NOT change the

ending of a polyatomic ion.ending of a polyatomic ion. Example: NaSCN – sodium thiocyanateExample: NaSCN – sodium thiocyanate Example: CaCOExample: CaCO33 – calcium carbonate – calcium carbonate

Example: NHExample: NH44Cl – ammonium chlorideCl – ammonium chloride

Transition Metals (except Transition Metals (except AgAg++, Zn, Zn+2+2, Cd, Cd+2+2))

Determine charge of cation by Determine charge of cation by looking at the formula and the anion.looking at the formula and the anion.

Name the cation, indicating charge Name the cation, indicating charge using Roman numerals in using Roman numerals in parentheses.parentheses.

Name the anion.Name the anion. Example: FeClExample: FeCl33 – iron (III) chloride – iron (III) chloride

Example: PbSOExample: PbSO44 – lead (II) sulfate – lead (II) sulfate

AcidsAcids

If the compound has an H as a If the compound has an H as a cation, it is usually an acid.cation, it is usually an acid.

HCl, HBr, HI, HCl, HBr, HI, HNOHNO33, , HClOHClO44, H, H22SOSO44 – Know these 6 strong acidsKnow these 6 strong acids

Naming acids Naming acids containing H and a containing H and a nonmetalnonmetal 1. Determine the root of the 1. Determine the root of the

nonmetal.nonmetal. 2. Place the prefix “hydro” in front of 2. Place the prefix “hydro” in front of

the base.the base. 3. Change the ending to –ic and add 3. Change the ending to –ic and add

the word “acid”the word “acid” Example: HCl: hydroExample: HCl: hydrochlorchloric acidic acid Example: Example: HBrHBr: hydrobromic acid: hydrobromic acid Example: HI: hydroiodic acidExample: HI: hydroiodic acid

Naming Acids Naming Acids containing polyatomic containing polyatomic ionsions Name the polyatomic ion, Name the polyatomic ion,

changing the ending as follows:changing the ending as follows:– -ate -ate -ic acid -ic acid– -ite -ite -ous acid -ous acid

Example: Example: HNOHNO33: nitric acid: nitric acid

Example: Example: HNOHNO22: nitrous acid: nitrous acid

Naming compounds Naming compounds containing 2 containing 2 nonmetalsnonmetals

Name the compound following the rules Name the compound following the rules for binary compounds and add prefixes for binary compounds and add prefixes to indicate the number of each atom in to indicate the number of each atom in the compound. the compound.

Prefixes:Prefixes:– Mono – 1Mono – 1 hexa - 6hexa - 6– Di- 2Di- 2 hepta - 7hepta - 7– Tri – 3Tri – 3 octa - 8octa - 8– Tetra – 4Tetra – 4 nona - 9nona - 9– Penta – 5Penta – 5 deca - 10deca - 10

Naming compounds Naming compounds containing 2 nonmetalscontaining 2 nonmetals

Example: Example: SS22OO88 : disulfur octoxide : disulfur octoxide

Example: Example: PP33NN55 : triphosphorous : triphosphorous

pentanitridepentanitride Example: CO: carbon monoxideExample: CO: carbon monoxide Example: CO2: carbon dioxideExample: CO2: carbon dioxide

Polyatomic IonsPolyatomic Ions Ions that consist of more than one atomIons that consist of more than one atom Know the ones for the quiz; list for othersKnow the ones for the quiz; list for others Naming of Pis with ONaming of Pis with O

– Most common form –Most common form –ate; ate; ClOClO33-- chlorate chlorate

– One less O: -One less O: -ite; ite; ClOClO22-- chlorite chlorite

– Two less O: Two less O: hypo<hypo<root>root>ite; ite; ClOClO-- hypochlorite hypochlorite

– One more O: One more O: perper<root><root>ate; ate; ClOClO44-- perchlorate perchlorate