atoms molecules and ionsatoms, molecules, and...

Atoms Molecules and IonsAtoms Molecules and IonsAtoms, Molecules, and IonsAtoms, Molecules, and Ions

Chemistry Timeline #1Chemistry Timeline #1B.C.400 B.C. Demokritos and Leucippos use the term "atomos”

2000 years of Alchemy

1500's Georg Bauer: systematic metallurgy Paracelsus: medicinal application of minerals

1600'sRobert Boyle:The Skeptical Chemist. Quantitative experimentation, identification of elements

1700s' Georg Stahl: Phlogiston Theory Joseph Priestly: Discovery of oxygen A t i L i i Th l f i b ti l f ti f Antoine Lavoisier: The role of oxygen in combustion, law of conservation of

mass, first modern chemistry textbook

Chemistry Timeline #2Chemistry Timeline #2

1800'sJoseph Proust: The law of definite proportion (composition) John Dalton: The Atomic Theory, The law of multiple proportionsJoseph Gay-Lussac: Combining volumes of gases, existence of diatomic moleculesAmadeo Avogadro: Molar volumes of gasesJons Jakob Berzelius: Relative atomic masses, modern symbols for the elements Dmitri Mendeleyev: The periodic table J.J. Thomson: discovery of the electron Henri Becquerel: Discovery of radioactivity

1900's1900 s Robert Millikan: Charge and mass of the electron Ernest Rutherford: Existence of the nucleus, and its relative size Meitner & Fermi: Sustained nuclear fission Ernest Lawrence: The cyclotron and trans-uranium elements Ernest Lawrence: The cyclotron and trans-uranium elements

Dalton’s Atomic Theory (1808)Dalton’s Atomic Theory (1808)

All matter is composed of extremely small particles called atoms Atoms of a given element are Atoms of a given element are identical in size, mass, and other properties; atoms of different l diff i i d

John Dalton

Atoms cannot be subdivided, created, or destroyed

elements differ in size, mass, and other properties

Atoms cannot be subdivided, created, or destroyed Atoms of different elements combine in simple whole-number ratios to form chemical compounds In chemical reactions atoms are combined In chemical reactions, atoms are combined, separated, or rearranged

Modern Atomic TheoryModern Atomic TheorySeveral changes have been made to Dalton’s theory.Dalton said:

Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size mass and different elements differ in size, mass, and other properties

Modern theory states:Modern theory statesAtoms of an element have a characteristic average mass which is unique to that lelement.

Modern Atomic Theory #2Modern Atomic Theory #2yy

Dalton said:

Modern theory states:

Atoms cannot be subdivided, created, or destroyed

Modern theory states:Atoms cannot be subdivided, created, or destroyed in ordinary chemical reactions. However, these y m . ,changes CAN occur in nuclear reactions!

Discovery of the ElectronDiscovery of the ElectronIn 1897 J J Thomson used a cathode ray tube In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle.

Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.y p

Thomson’s Atomic ModelThomson’s Atomic Model

h b l d h h l l k l Thomson believed that the electrons were like plums embedded in a positively charged “pudding,” thus it was called the “plum pudding” model.p p g

Mass of the ElectronMass of the Electron

1909 – Robert Millikan determines the mass of the electron.

The oil drop apparatusMass of the electron is 9.109 x 10-31 kg

Conclusions from the Study of Conclusions from the Study of th El tth El tthe Electronthe Electron

Cathode rays have identical properties regardless Cathode rays have identical properties regardless of the element used to produce them. All elements must contain identically charged electrons.Atoms are neutral so there must be positive Atoms are neutral, so there must be positive particles in the atom to balance the negative charge of the electrons Electrons have so little mass that atoms must contain other particles that account for most of the massthe mass

Rutherford’s Gold Foil ExperimentRutherford’s Gold Foil Experiment

Alpha particles are helium nuclei Particles were fired at a thin sheet of gold foil P ti l hit th d t ti (fil ) Particle hits on the detecting screen (film) are recorded

Try it Yourself!Try it Yourself!I th f ll i i t th i t t hidd b In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target?

The AnswersThe Answers

Target #1 Target #2

Rutherford’s FindingsRutherford’s Findings M t f th ti l d i ht th h Most of the particles passed right through A few particles were deflected VERY FEW were greatly deflectedg y

“Like howitzer shells bouncing off of tissue paper!”of tissue paper!

The nucleus is small

Conclusions:

The nucleus is dense The nucleus is positively charged

Atomic ParticlesAtomic ParticlesAtomic ParticlesAtomic ParticlesParticle Charge Mass (kg) LocationEl t 1 9 109 10 31 El t Electron -1 9.109 x 10-31 Electron

cloud

Proton +1 1.673 x 10-27 Nucleus

Neutron 0 1.675 x 10-27 Nucleus

The Atomic The Atomic ScaleScale

Most of the mass of the atom is in the nucleus (protons and neutrons)(protons and neutrons) Electrons are found outside of the nucleus (the l t l d)electron cloud) Most of the volume of the atom is empty spacep y p

“q” is a particle called a “quark”q is a particle called a quark

About Quarks…About Quarks…Protons and neutrons are NOT fundamental particles.

Protons are made of two “up” quarks and one “down” quarkone down quark.

Neutrons are made of one “up” quark and one up quark and two “down” quarks.

Quarks are held togetherQuarks are held togetherby “gluons”

IsotopesIsotopesI t t f th l t h i Isotopes are atoms of the same element having different masses due to varying numbers of neutrons.

Isotope Protons Electrons Neutrons NucleusIsotope Protons Electrons Neutrons Nucleus

Hydrogen–1(protium)

1 1 0(protium)

Hydrogen-2(d t i )

1 1 1(deuterium)

Hydrogen-3 1 1 2y g(tritium)

Atomic MassesAtomic MassesAtomic mass is the average of all the naturally

Isotope Symbol Composition of % in nature

g yisotopes of that element. Carbon = 12.011Isotope Symbol Composition of

the nucleus% in nature

Carbon-12 12C 6 protons 98.89%6 neutrons

Carbon-13 13C 6 protons 1.11%7 neutrons

Carbon-14 14C 6 protons <0.01%p8 neutrons

Atomic NumberAtomic NumberAtomic number (Z) of an element is the number of protons in the nucleus of each atom f th t l tof that element.

Element # of protons Atomic # (Z)

Carbon 6 6

Phosphorus 15 15

Gold 79 79

Mass NumberMass NumberMass number is the number of protons and Mass number is the number of protons and neutrons in the nucleus of an isotope.

Mass # = p+ + n0

Nuclide p+ n0 e- Mass #Oxygen 108 8 1818Oxygen - 10

- 33 42

31 15

8 8 1818Arsenic 75 33 75Ph h 15 116- 31 15Phosphorus 15 3116

MoleculesMoleculesTwo or more atoms of the same or different elements, covalently bonded together.elements, covalently bonded together.

Molecules are discrete structures, and their formulas represent each atom present in the formulas represent each atom present in the molecule.

Benzene, C6H6, 6 6

Covalent Network SubstancesCovalent Network SubstancesCovalent network substances have covalently bonded atoms, but do not have discrete formulas.

Why Not??Graphite Diamond

IonsIonsIonsIons CationCation: A positive ion: A positive ion

•• MgMg2+2+, NH, NH44++

AnionAnion: A negative ion: A negative ion ClCl, SO, SO44

22

Ionic BondingIonic Bonding: Force of attraction between : Force of attraction between oppositely charged ions.oppositely charged ions.

Ionic compounds form Ionic compounds form crystalscrystals, so their , so their formulas are written formulas are written empirically empirically (lowest whole (lowest whole number ratio of ions).number ratio of ions).number ratio of ions).number ratio of ions).

Periodic Table with Periodic Table with Group Names

The Properties of a Group: the Alkali Metalsthe Alkali Metals

Easily lose valence electron (Reducing agents)R t i l tl ith tReact violently with waterLarge hydration energyReact with halogens to form saltsReact with halogens to form salts

Predicting Ionic ChargesPredicting Ionic ChargesGroup 1Group 1:: Lose 1 electron to form Lose 1 electron to form 1+1+ ionsions

HH++ LiLi++ NaNa++ KK++HH LiLi NaNa KK

Predicting Ionic ChargesPredicting Ionic ChargesGroup 2Group 2:: Loses 2 electrons to form Loses 2 electrons to form 2+2+ ionsions

BeBe2+2+ MgMg2+2+ CaCa2+2+ SrSr2+2+ BaBa2+2+BeBe MgMg CaCa SrSr BaBa

Predicting Ionic ChargesPredicting Ionic ChargesG 13G 13 L 3 L 3 Group 13Group 13:: Loses 3 Loses 3 electrons to form electrons to form 3+3+ ionsions

BB3+3+ AlAl3+3+ GaGa3+3+

3+3+ ionsions

Predicting Ionic ChargesPredicting Ionic ChargesG 14G 14 L 4 L 4 Group 14Group 14:: Loses 4 Loses 4 electrons or gains electrons or gains 4 electrons4 electrons

Caution! Caution! CC2222-- and Cand C44--

are both called are both called carbidecarbide4 electrons4 electrons

Predicting Ionic ChargesPredicting Ionic ChargesG 15G 15 G i 3 G i 3 NN33-- Nitride Group 15Group 15:: Gains 3 Gains 3 electrons to form electrons to form 33-- ionsions

NN33--

PP33--

AsAs33--

NitridePhosphideArsenide 33-- ionsionsAsAs33-- Arsenide

Predicting Ionic ChargesPredicting Ionic ChargesG 16G 16 G i 2 G i 2 OO22-- Oxide Group 16Group 16:: Gains 2 Gains 2 electrons to form electrons to form 22-- ionsions

OO22--

SS22--

SeSe22--

OxideSulfideSelenide 22-- ionsionsSeSe22-- Selenide

Predicting Ionic ChargesPredicting Ionic ChargesG 17G 17 G i 1 G i 1 FF11-- BrBr11--Fluoride Bromide Group 17Group 17:: Gains 1 Gains 1 electron to form electron to form 11-- ionsions

FF11--

ClCl11--BrBr11--Fluoride

Chloride

Bromide

II11-- Iodide11-- ionsions

Predicting Ionic ChargesPredicting Ionic ChargesG 18G 18 St bl St bl Group 18Group 18:: Stable Stable Noble gases Noble gases do notdo notform ions!form ions!form ions!form ions!

Predicting Ionic ChargesPredicting Ionic ChargesGroups 3 Groups 3 -- 1212:: Many Many transitiontransition elements elements Groups 3 Groups 3 -- 1212:: Many Many transitiontransition elements elements have more than one possible oxidation state.have more than one possible oxidation state.Iron(II) = Fe2+ Iron(III) = Fe3+Iron(II) = Fe2+ Iron(III) = Fe3+

Predicting Ionic ChargesPredicting Ionic ChargesGroups 3 Groups 3 -- 1212:: Some Some transitiontransition elements elements Groups 3 Groups 3 -- 1212:: Some Some transitiontransition elements elements have only one possible oxidation state.have only one possible oxidation state.Zinc = Zn2+ Silver = Ag+Zinc = Zn2+ Silver = Ag+

Writing Ionic Compound FormulasWriting Ionic Compound FormulasExample: Barium nitrate

1. Write the formulas for the cation f fand anion, including CHARGES!

BaBa2+2+ NONO --2. Check to see if charges are ( )( )BaBa2+2+ NONO33--. f g

balanced.

3. Balance charges , if necessary, Not balanced!

( )( )223. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ionpolyatomic ion.

Writing Ionic Compound FormulasWriting Ionic Compound FormulasExample: Ammonium sulfate


NHNH ++ SOSO 22--2. Check to see if charges ( )( )NHNH44 SOSO4422. f g

are balanced.

3. Balance charges , if necessary,

( )( )22

3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion

Not balanced!

polyatomic ion.

Writing Ionic Compound FormulasWriting Ionic Compound FormulasExample: Iron(III) chloride


FeFe3+3+ ClCl--2. Check to see if charges FeFe33 ClCl. f gare balanced.

3. Balance charges , if necessary, Not balanced!


Not balanced!

polyatomic ion.

Writing Ionic Compound FormulasWriting Ionic Compound FormulasExample: Aluminum sulfide


AlAl3+3+ SS22--2. Check to see if charges AlAl3+3+ SS22--. f gare balanced.

3. Balance charges , if necessary, 22 33


Not balanced!

polyatomic ion.

Writing Ionic Compound FormulasWriting Ionic Compound FormulasExample: Magnesium carbonate


MgMg2+2+ COCO 22--2. Check to see if charges MgMg22 COCO3322. f g

are balanced.

h b l d!They are balanced!

Writing Ionic Compound FormulasWriting Ionic Compound FormulasExample: Zinc hydroxide


ZnZn2+2+ OHOH--2. Check to see if charges are ( )( )ZnZn2+2+ OHOH--. f gbalanced.

3. Balance charges , if necessary,

( )( )223. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion

Not balanced!

polyatomic ion.

Writing Ionic Compound FormulasWriting Ionic Compound FormulasExample: Aluminum phosphate


AlAl3+3+ POPO 33--2. Check to see if charges are AlAl3+3+ POPO4433--. f g

balanced.

They ARE balanced!

Naming Ionic CompoundsNaming Ionic CompoundsNaming Ionic CompoundsNaming Ionic Compounds•• 1. Cation first, then anion1. Cation first, then anion

•• 2 Monatomic cation = name of the element2 Monatomic cation = name of the element•• 2. Monatomic cation = name of the element2. Monatomic cation = name of the element•• CaCa2+2+ = calcium= calcium ionion

•• 3. Monatomic anion = 3. Monatomic anion = rootroot + + --ideide•• ClCl = chlor= chlorideide

•• CaClCaCl22 = calcium chlor= calcium chlorideide

Naming Ionic CompoundsNaming Ionic CompoundsNaming Ionic CompoundsNaming Ionic Compoundsg pg p(continued)(continued)

g pg p(continued)(continued)

Metals with multiple oxidation statesMetals with multiple oxidation states some metal forms more than one some metal forms more than one cationcation use use Roman numeralRoman numeral in namein name

pp

use use Roman numeralRoman numeral in namein name

PbClPbCl22

PbPb2+2+ is the lead(is the lead(IIII) cation) cation

PbClPbCl22 = lead(= lead(IIII) chloride) chloride

Naming Binary CompoundsNaming Binary CompoundsNaming Binary CompoundsNaming Binary Compoundsg y pg y pg y pg y p Compounds between two Compounds between two nonmetalsnonmetals First element First element in the formula is in the formula is named firstnamed first.. Second element Second element is named as if it were an is named as if it were an anionanion.. Use prefixesUse prefixes Only use Only use monomono on second element on second element --

PP22OO55 == didiphosphorus phosphorus pentpentoxideoxide55

COCO22 ==CO =CO =

p pp p ppcarbon carbon didioxideoxidecarbon carbon monmonoxideoxide

NN22O =O = didinitrogen nitrogen monmonoxideoxide

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