Chapter 2: Atoms, Molecules and Ions

Chem 106, Prof. J.T. SpencerChem 106, Prof. J.T. Spencer

11

What is ChemistryWhat is Chemistry

Chapter 2: Atoms, Molecules and IonsChapter 2: Atoms, Molecules and Ions

Chapt. 2.1

MagicMagicLogicLogic


22

Science: Atomic TheoryScience: Atomic Theory

– “The strength of a science is that its conclusions The strength of a science is that its conclusions are derived by logical arguments from facts that are derived by logical arguments from facts that result from well-designed experiments. Science result from well-designed experiments. Science has produced a picture of the microscopic has produced a picture of the microscopic structure of the atom so detailed and subtle of structure of the atom so detailed and subtle of something so far removed from our immediate something so far removed from our immediate experience that it is difficult to see how its many experience that it is difficult to see how its many features were constructed. This is because so features were constructed. This is because so many experiments have contributed to our ideas many experiments have contributed to our ideas about the atom.about the atom.”

B. Mahan from University Chemistry

Atoms, Molecules and IonsAtoms, Molecules and Ions

Chapt. 2.1


33

MacroscopicMacroscopic Microscopic MicroscopicSubstances Atomic theoryMixturesPhysical Properties and Changes

Science: Atomic TheoryScience: Atomic Theory– from a fundamental understanding of the

macroscopic behavior of substances comes an understanding the microscopic behavior of atoms and molecules (Baseball rules from Baseball Game?)


Chapt. 2.1

Question: Can matter be infinitely divided?Most Greek Philosophers - Yes

Democritus (460 BC) and John Dalton (1800s) - No (“atomos”means indivisible”)


44


Chapt. 2.1

History of Atomic Theory and Scientific InquiryHistory of Atomic Theory and Scientific Inquiry

– Aristotle - “metaphysics”, thought experiments and no experimental observations

necessary to substantiate ideas.

– Archimedes (287 - 212 BC) - Scientific Method, determined composition of the King of Syracuse’s crown by measuring density through water displacement.

– Roger Bacon (1214 - 1294) - Experimental Science “ It is the credo of free men - the opportunity to try, the privilege to err, the courage to experiment anew. ...experiment, experiment, ever experiment”.


55

Archimedes was a native of Syracuse (not NY). Stories from Plutarch, Livy, and others describe machines invented by Archimedes for the defence of Syracuse (These include the catapult, the compound pulley and a burning-mirror).

Archimedes discovered fundamental theorems concerning the centre of gravity of plane figures and solids. His most famous theorem gives the weight of a body immersed in a liquid, called Archimedes' principal.

Archimedes (287-212BC)Archimedes (287-212BC)

His methods anticipated integral calculus 2,000 years before Newton and Leibniz.


66Archimedes (287-212BC)Archimedes (287-212BC)


77

Suspecting that a goldsmith might have replaced some of the gold by silver in making a crown, Hiero II, the king of Syracuse, asked Archimedes to determine whether the wreath was pure gold. The wreath could not be harmed since it was a holy object.

The solution which occurred when he stepped into his bath and caused it to overflow was to put a weight of gold equal to the crown, and known to be pure, into a bowl which was filled with water to the brim. Then the gold would be removed and the king's crown put in, in its place. An alloy of lighter silver would increase the bulk of the crown and cause the bowl to overflow.

Equal Weight of Gold Crown Displaced More Water

Archimedes (287-212BC)Archimedes (287-212BC)

Pure Gold?


88Greek PhilosophersGreek Philosophers

DemocratusDemocratus - First to say that all matter is - First to say that all matter is NOT infinately divisible. [But the NOT infinately divisible. [But the Greeks did not test their ideas]Greeks did not test their ideas]

AlchemyAlchemy - Pseudoscience by fakes and mystics - Pseudoscience by fakes and mystics devoted to turning base metals to gold BUT they devoted to turning base metals to gold BUT they did make (by accident) many ground breaking did make (by accident) many ground breaking discoveries of nature (chemical reactions).discoveries of nature (chemical reactions).

EarthEarth

AirAirFireFire

WaterWater

Greek “Elements”Greek “Elements”


99Scientific MeasurementScientific Measurement

Robert BoyleRobert Boyle - - Robert Boyle Robert Boyle (1627-1691) was born in Ireland. (1627-1691) was born in Ireland. He became especially interested in He became especially interested in experiments involving air and experiments involving air and developed an air pump with which developed an air pump with which he produced evacuated cylinders. he produced evacuated cylinders. He used these cylinders to show He used these cylinders to show that a feather and a lump of lead that a feather and a lump of lead

fall fall at the same rate in the absence of at the same rate in the absence of air resistance. In his book “The Sceptical Chemist” air resistance. In his book “The Sceptical Chemist” (1661), Boyle urged that the ancient view of elements as (1661), Boyle urged that the ancient view of elements as mystical substances should be abandoned and that an mystical substances should be abandoned and that an element should instead be defined as anything that element should instead be defined as anything that cannot be broken down into simpler substances.cannot be broken down into simpler substances.


1010Scientific MeasurementScientific Measurement

Antoine LavoisierAntoine Lavoisier (1743 - 1794) - (1743 - 1794) - Furthered measurement as basis for Furthered measurement as basis for scientific reasoning. scientific reasoning.

– ““Je Veux Parler Des Faits” Je Veux Parler Des Faits” - Do Not Rely Upon Speculation But Build Upon Facts.

More on Lavoisier on Next SlideMore on Lavoisier on Next Slide


1111Antoine LavoisierAntoine Lavoisier

Antoine Lavoisier Antoine Lavoisier was born in was born in Paris, and although Lavoisier's Paris, and although Lavoisier's father wanted him to be a father wanted him to be a lawyer, Lavoisier was lawyer, Lavoisier was fascinated by science. From the fascinated by science. From the beginning of his scientific beginning of his scientific career, Lavoisier recognized the career, Lavoisier recognized the importance of accurate importance of accurate

measurements. He wrote the measurements. He wrote the first modern chemistryfirst modern chemistry (1789) (1789) textbook so that it is not surprising that Lavoisier is often called the textbook so that it is not surprising that Lavoisier is often called the father of modern chemistry. To help support his scientific work, father of modern chemistry. To help support his scientific work, Lavoisier invested in a private tax-collecting firm and married the Lavoisier invested in a private tax-collecting firm and married the daughter of one of the company executives. Guillotined for his tax daughter of one of the company executives. Guillotined for his tax work in 1794.work in 1794.


1212


Chapt. 2.1

pure water evaporate out water fromdust sealed container

“earth”

alchemists said that the water was “transmuted” to earth

Lavoisier showed that the amount of “earth” found at theend of the experiment was equal to the weight the containerlost, therefore, the water was not “transmuted” to earth.

Earth

FireWater

AlchemyAlchemy

History Atomic Theory and Scientific InquiryHistory Atomic Theory and Scientific Inquiry

– Lavoisier (1743 - 1794) - founder of “modern chemistry”, not to rely on speculation but to build upon facts, ended the “time of alchemy”.

Law of Conservation of Mass


1313

Scientific MethodScientific Method

Chapt. 2.1

ObservationsObservationsand Experimentsand Experiments

Patterns and Patterns and TrendsTrends

Form and testForm and testhypothesishypothesis

TheoryTheory


1414John Dalton (1766-1844)John Dalton (1766-1844)

John DaltonJohn Dalton (1766 -1844), an (1766 -1844), an Englishman, began teaching school Englishman, began teaching school when he was 12. He was fascinated when he was 12. He was fascinated with meteorology (keeping daily with meteorology (keeping daily weather records for 46 years), which weather records for 46 years), which led to an interest in gases and their led to an interest in gases and their components, atoms. He switched to components, atoms. He switched to chemistry when he saw applications in chemistry when he saw applications in

chemistry for his ideas about the atmosphere. He proposed chemistry for his ideas about the atmosphere. He proposed the the Atomic TheoryAtomic Theory in 1803. Dalton was a humble man with in 1803. Dalton was a humble man with several apparent handicaps: he was poor; he was not several apparent handicaps: he was poor; he was not articulate; he was not a skilled experimentalist, and he was articulate; he was not a skilled experimentalist, and he was color-blind (a terrible problem for a chemist). In spite of these color-blind (a terrible problem for a chemist). In spite of these disadvantages he did great things.disadvantages he did great things.


1515

John Dalton’s Atomic TheoryJohn Dalton’s Atomic Theory

–Designed a theory to account for a variety of experimental observations:

–Each element is composed of extremely small particles (called atoms).

–All atoms of a given element are identical (therefore, atoms of different elements are different and have different properties).

Atomic TheoryAtomic Theory

Chapt. 2.1


1616

John Dalton’s Atomic TheoryJohn Dalton’s Atomic Theory

–Atoms of an element are not changed into different types of atoms by chemical reactions and atoms are neither created nor destroyed in chemical reactions.

–Compounds are formed when atoms combine and a given compound always has the same relative number and kind of atoms.

Atomic Theory (Continued)Atomic Theory (Continued)

Chapt. 2.1


1717

Dalton’s Atomic TheoryDalton’s Atomic Theory

–Atoms are the building blocks:

–ElementsElements are composed of only one kind of atom.

–CompoundsCompounds are made by mixing atoms in definite proportions

–MixturesMixtures do not involve the type of “small scale” (but strong) interactions found in Elements and Compounds

Atomic TheoryAtomic Theory

Chapt. 2.1


1818

Law of Constant Composition Law of Constant Composition (or Definite (or Definite Proportion, first proposed by Joseph Proust)Proportion, first proposed by Joseph Proust)::– In any given compound, the relative number

and kind of atoms are constant (same proportion of elements by mass).

–implies that atoms interact in a specific way when they form a compound.

–the elements making up a particular compound combine in the same proportions regardless of the manner in which the compound was prepared.

Atomic Theory; Dalton’s TheoriesAtomic Theory; Dalton’s Theories

Chapt. 2.1


1919

Law of Constant Composition (or Definite Law of Constant Composition (or Definite Proportion):Proportion):


Chapt. 2.1

Copper Carbonate ALWAYS contains 5.3 parts Copper Carbonate ALWAYS contains 5.3 parts Copper to 4 parts Oxygen and 1 part Carbon (by Copper to 4 parts Oxygen and 1 part Carbon (by Weight).Weight).

Carbon Dioxide ALWAYS contains 1.00 parts Carbon Dioxide ALWAYS contains 1.00 parts Carbon to 2.67 parts OxygenCarbon to 2.67 parts Oxygen


2020

Law of Conservation of Mass:Law of Conservation of Mass:

– the total amount of material present after a chemical reaction is the same as the amount present before the reaction.


Chapt. 2.1

Matter (elements, etc...) cannot be created nor Matter (elements, etc...) cannot be created nor destroyed during chemical reactions.destroyed during chemical reactions.

Total Mass Before

Chemical Reaction

Total Mass After

Chemical Reaction

==


2121Guy-Lussac

Joseph Guy-Lussac (1778 - 1850) found that (at the same temperatures and pressures):

2 volumes of hydrogen reacts with 1 volume of oxygen to yield 1 volume of water vapor

O H Water+ =

Amedeo Avogadro (1776 - 1856) proposed that (at the same temperatures and pressures), equal volumes of different gases contain the same number of particles:

2 molecules of H + 1 molecule of O yield 1 molecule of water


2222Experiments in Atomic TheoryExperiments in Atomic Theory

FaradayFaraday - Electrodeposition - Electrodeposition MillikanMillikan - Oil Drop Experiment - Oil Drop Experiment RoetgenRoetgen - Radioactivity - Radioactivity CurieCurie - Radioactive Particles - Radioactive Particles RutherfordRutherford - Gold Foil Experiment - Gold Foil Experiment

Dalton’s Laws Set Groundwork for Atomic Theory but Dalton’s Laws Set Groundwork for Atomic Theory but Important Experiments Lead to Our Modern Important Experiments Lead to Our Modern

UnderstandingUnderstanding


2323Michael Faraday (1791-1867)Michael Faraday (1791-1867)

Experiments in electro-Experiments in electro-magnetism, electrical power magnetism, electrical power conversion, etc...conversion, etc...Humble scientist rose from Humble scientist rose from very poor background to very poor background to become one of the most become one of the most influential of his age. Believed influential of his age. Believed that careful observations were that careful observations were most important.most important.

““Try desperately to succeed - Try desperately to succeed - and do not hope for success”and do not hope for success”


2424

Electrical NatureElectrical Nature

–Michael Faraday (1833) (first ideas about the nature of electricity

–The weight of a material The weight of a material deposited at an electrode by a deposited at an electrode by a given amount of electricity is given amount of electricity is always the same.always the same.

–The weights of various The weights of various materials deposited by fixed materials deposited by fixed amounts of electricity are amounts of electricity are proportional to their proportional to their equivalent weightsequivalent weights. . [remember [remember equivalent weights]equivalent weights]

Chapt. 2.1

Atomic StructureAtomic Structure

electrodes

deposition electrolyte

+-

ElectrodepositionElectrodepositionCellCell


2525Sir J. J. ThomsonSir J. J. Thomson

British physicist who British physicist who worked with electrical worked with electrical currents and fields.currents and fields.

Appointed Prof. of Physics Appointed Prof. of Physics at Cambridge when at Cambridge when he was 27 and he was 27 and

Received the Nobel Proze in Received the Nobel Proze in 1906 for his 1906 for his characterization of characterization of the electron.the electron.


2626

J. J. ThomsonJ. J. Thomson: Cathode Ray Tube (CRT) Experiment: Cathode Ray Tube (CRT) Experiment

– Set up a large electrical potential between a pair of electrodes in a glass tube and an electrical current will flow between the elctrodes.

–The current will flow even when all the air is pumped out of the tube. The invisible charge carriers were called “cathode rays”.

–Cathode rays travel in straight lines and form a luminious spot when they hit a glass tube.

Chapt. 2.1

Atomic StructureAtomic Structure

(-)(-) (+)(+)

Cathode Ray TubeCathode Ray Tube[evacuated glass tube][evacuated glass tube]


2727

(-)(-) (+)(+)

(-)(-) (+)(+)

Electric Field

Magnetic FieldChapt. 2.1

Atomic Structure: CRTAtomic Structure: CRT

The cathode rays are deflected by an electric field.

The same effect was observed regardless of what gas was used in the discharge tube. Therefore, electricity must be a universal fragment.

The cathode rays are deflected by an magnetic field.


2828

(-)(-)(+)(+)

Electric Field

Chapt. 2.1

Electricity: Thomson’s charge to massElectricity: Thomson’s charge to mass

Magnetic Field

123

Spot mag field elec. field

1 On Off3 Off On2 Off Off

On On

CRTCRT (-)(-)

(+)(+)


2929

Ee = Electrical FieldEe = Electrical Field HeHe = Magnetic Field = Magnetic Field[where e = electric charge (unk) and [where e = electric charge (unk) and = velocity] = velocity]

Set up experiment such that;Set up experiment such that;Electrical Field = Magnetic Field Electrical Field = Magnetic Field

Ee = HeEe = Heoror

E / HE / HNow, turn off the mag. field and measure deflection of beam (Now, turn off the mag. field and measure deflection of beam ())

Using Newton’s 2nd Law can calculate e/mUsing Newton’s 2nd Law can calculate e/m

Thomson’s charge to massThomson’s charge to mass

(-)(-)(+)(+)

Magnetic Field

123

CRTCRT (-)(-)

(+)(+)


3030Thomson’s charge to massThomson’s charge to mass

calculated charge to mass ratio (e/m) for electron = 1.76 x 108 coulombs/gfound;

(1) e/m was 1000x greater than for any known ion(2) e/m of independent of gas in tube [Universal Fragment](3) Not electrified atoms but fragments (called electrons)


3131

Nobel Prize, 1923; for his work on Nobel Prize, 1923; for his work on the elementary charge of electricity the elementary charge of electricity and on the photoelectric effect. and on the photoelectric effect.

Robert Millikan was one of Robert Millikan was one of the first American scientists to be the first American scientists to be recognized in Europe. In 1909 he recognized in Europe. In 1909 he performed the first of a series of performed the first of a series of experiments to measure the experiments to measure the

fundamental charge of an fundamental charge of an electron, electron, the Millikan Oil Drop the Millikan Oil Drop Experiment. The value determined by this experiment was used Experiment. The value determined by this experiment was used in Bohr's formula for the energy of the Hydrogen line spectrum in Bohr's formula for the energy of the Hydrogen line spectrum as a first confirmation of the quantized atom. He named and as a first confirmation of the quantized atom. He named and studied "cosmic rays" as well.studied "cosmic rays" as well.

Robert Millikan (1868-1953)Robert Millikan (1868-1953)


3232

Chapt. 2.1

Electricity: Millikan’s electron massElectricity: Millikan’s electron mass

++

--

viewer

Oil Drop Experiment (1909)Oil Drop Experiment (1909)

atomizer

highvoltage

Goal: to measure the electrical charge on each oil droplet

Procedure: measure the velocity of the falling oil drop both with and without the high voltage plates urned on

Found: charges were always multiples of 1.60 x 10-19 C

Postulate: charge of one electron was 1.60 x 10-19 CIonization by radiation causes

the oil to pick up “extra” electrons


3333

Chapt. 2.1

Electricity: electron massElectricity: electron mass

charge= e = 1.76 x 108 coul g-1

mass mThomsonThomson

MillikanMillikan

Combine and SolveCombine and Solve

charge = e = 1.60 x 10-19 coul

mass = charge = 1.60 x 10-19 C = 9.10 x 10-28 g 1.76 x 108 coul g-1 1.76 x 108 C g-1

mass of the electron was 2000x smaller than the lightest atom (hydrogen)


3434Wilhelm Conrad RoentgenWilhelm Conrad Roentgen

Wilhelm Conrad Roentgen was born in Wilhelm Conrad Roentgen was born in Lennep, Germany, on 27 March 1845. He Lennep, Germany, on 27 March 1845. He obtained a degree in mechanical obtained a degree in mechanical engineering and, in 1869, was awarded a engineering and, in 1869, was awarded a degree in physics. While working as a degree in physics. While working as a professor of physics at Wurzburg professor of physics at Wurzburg University, he made his famous discovery. University, he made his famous discovery. He called the unknown radiation "X rays," He called the unknown radiation "X rays," since "X" frequently stands for an since "X" frequently stands for an unknown quantity in mathematics. His unknown quantity in mathematics. His unique discovery truly changed the world unique discovery truly changed the world and immediately became a useful tool for and immediately became a useful tool for medical science.medical science.

Wilhelm Conrad Wilhelm Conrad RoentgenRoentgen


3535

Chapt. 2.1

Radioactivity: Radioactivity: Wilhelm Roetgen and Henri BecquerelWilhelm Roetgen and Henri Becquerel

CRTCRT metaltarget

e beam

invisibleinvisibleradiation radiation (X-rays)(X-rays)

X-raysX-rays- not affected by magnetic fields- passed thru many materials-produced images on film

(ionized Ag emulsions)U glowed in dark (phosphorescence)

emitted high energyradiation in the dark (radioactivity)


36361903 Nobel Prize for Radioactivity1903 Nobel Prize for Radioactivity

Pierre and Marie CuriePierre and Marie Curie Henri BecquerelHenri Becquerel


3737

The most famous of all women scientists, The most famous of all women scientists, Marie Sklodowska-Curie is notable for many Marie Sklodowska-Curie is notable for many firsts. firsts.

In 1903, she became the first woman to win a In 1903, she became the first woman to win a Nobel Prize for Physics (Pierre Curie Nobel Prize for Physics (Pierre Curie and Henri Becquerel, for the discovery and Henri Becquerel, for the discovery of radioactivity.of radioactivity.

She was also a professor at the Sorbonne She was also a professor at the Sorbonne University in Paris (1906). University in Paris (1906).

In 1911, she won an unprecedented second In 1911, she won an unprecedented second Nobel Prize (in chemistry for her Nobel Prize (in chemistry for her discovery radium. She was the first discovery radium. She was the first person ever to receive two Nobel person ever to receive two Nobel Prizes.)Prizes.)

She was the first mother of a Nobel Prize She was the first mother of a Nobel Prize Laureate; daughter- Nobel Prize 1932.Laureate; daughter- Nobel Prize 1932.

Marie Sklodawaska CurieMarie Sklodawaska Curie

Marie Sklodowska-CurieMarie Sklodowska-CurieIn 1934, Maria Curie died of leukemiaIn 1934, Maria Curie died of leukemia


3838

Marie Curie (1867 - 1934) - separated the pure radioactive material (Uranium) which was spontaneously radioactive (from the mineral pitchblende)

Ernest Rutheford (1871 - 1937) - found radiation from uranium was of three types (, , and )

Chapt. 2.1

Radioactivity: Radioactivity: Marie Curie and Ernest RuthefordMarie Curie and Ernest Rutheford

slitsU

-

+

- heavy particles with +2 charge, combines with electrons

to form helium, 4He - electrons with -1 charge - high energy electromagnetic radiation


3939

Since the electron made up only a small amount of an atom’s mass it was proposed that it must similarly make up a small amount of the atoms volume.

Nuclear Atom: Nuclear Atom: Thomson’s Model (ca. 1900)Thomson’s Model (ca. 1900)

“Plum-pudding” model

= electron

positive charge spread over sphere


4040

Ernest Rutherford (1871-1937) was Ernest Rutherford (1871-1937) was born on a farm in New Zealand. In born on a farm in New Zealand. In 1895 he placed second in a 1895 he placed second in a scholarship competition to attend scholarship competition to attend Cambridge University, but was Cambridge University, but was awarded the scholarship when the awarded the scholarship when the winner decided to stay home and get winner decided to stay home and get married. As a scientist in England, married. As a scientist in England, Rutherford did much of the early Rutherford did much of the early work on characterizing work on characterizing radioactivity. He also invented the radioactivity. He also invented the

name proton for the nucleus of the hydrogen atom. He received name proton for the nucleus of the hydrogen atom. He received the Nobel Prize in chemistry in 1908.the Nobel Prize in chemistry in 1908.

Ernest RutherfordErnest Rutherford


4141Nuclear Atom: Nuclear Atom: Rutheford and the Gold FoilRutheford and the Gold Foil

slits

thin gold foil

4He particles

detector

“...as if you fired a 15-inch cannon shell at a piece of tissue paper and it came back and hit you...”

foundfound - most particles passed straight through foil, some had deflections thru small angles BUT some had VERY large deflections ( = 180°)

experimentexperiment - fired heavy particles at a thin gold foil and lookedfor deflections


4242Nuclear Atom: Nuclear Atom: Rutheford and the Gold FoilRutheford and the Gold Foil

Gold FoilGold Foil

A

A

A

A

CBB

BeamBeam

A:C around 13,000:1A:C around 13,000:1


4343

Based on gold foil experiment and previous work with electrical and nuclear particles, proposed a nuclear theory;

(1) atoms are mostly empty space with very dense (pos. charged) nuclear core (<10-12 cm dia.)

(2) atoms are highly “non-uniform”

(3 ) atomic nucleus must contain large electrical forces of considerable mass (since small electron cannot be responsible for such large deflections)

Rutheford’s AtomRutheford’s Atom


4444Nature’s Basic ForcesNature’s Basic Forces

ElectromagneticElectromagnetic - force between charged or magnetic particles (electrical and magnetic forces are very closely related). DRIVES MOST OF CHEMICAL BEHAVIOR (Coulomb’s Law; F = kQ1Q2/d2)

GravitationalGravitational - force between objects proportional to their masses.

Strong NuclearStrong Nuclear - force keeping like charged nucleons (such as protons) together (very strong but very short range).

Weak NuclearWeak Nuclear - nuclear force observed in some radioactive behavior (weaker than electromagnetic but stronger than gravitational).

+ -

m m

++ ++

Strong Nucl. > Electromagnetic > Weak Nucl. > GravitationalStrong Nucl. > Electromagnetic > Weak Nucl. > Gravitational


4545Modern Atomic StructureModern Atomic Structure atomic dimensions; nucleus 10atomic dimensions; nucleus 10-4-4 Å and atom 1 - 2 Å Å and atom 1 - 2 Å

(1 Å = 10 (1 Å = 10-10-10 m) “... if a nucleus were 2 cm (ca. 1 m) “... if a nucleus were 2 cm (ca. 1 in.)in.) then the atom would be 200 m (ca. 200 yds)” then the atom would be 200 m (ca. 200 yds)”

atom composed of many “subatomic” particles but only atom composed of many “subatomic” particles but only three of these are important to chemiststhree of these are important to chemists

atomic mass (1 amu = 4 x 10atomic mass (1 amu = 4 x 10-22-22 g), charge g), charge (1 esc = 1.60 x 10(1 esc = 1.60 x 10-19-19 coul), density (10 coul), density (101414 g/cm g/cm33))

atom = dense nucleus with mostly empty space; electrons of atom = dense nucleus with mostly empty space; electrons of most chemical import. (matchbox of nucl. = 2.5 billion tons)most chemical import. (matchbox of nucl. = 2.5 billion tons)

particle charge (esu) mass (amu)proton +1 1.0073neutron 0 1.0087electron -1 5.486 x 10-4


4646

Atomic Theory: IsotopesAtomic Theory: Isotopes differences/similarities between atoms of an element;differences/similarities between atoms of an element;

all atoms of an given element have the same number all atoms of an given element have the same number of protons (and therefore the same number of of protons (and therefore the same number of electrons to balance charge)electrons to balance charge)

atoms of an element may have different numbers of atoms of an element may have different numbers of neutrons - calledneutrons - called isotopes isotopes

atomic number (Z) - number of protonsmass number (A) - number of protons + number of neutronsnuclide - atoms of a specific elemental isotope

AE 11C 12C 13C 14CZ 6 6 6 6


4747

7 electrons, 7 protons, 7 neutrons




Atomic Theory: IsotopesAtomic Theory: Isotopes

14N7

17O8

35Cl17

238U92


4848

Sample exercise:How many protons, neutrons, and electrons are in a 39K atom?



4949

Sample exercise:How many protons, neutrons, and electrons are in a 39K atom?

Atomic# = 19 # of protons = 19

# of electrons = 19

Mass # = 39 39 - 19 = 20 neutrons



5050

Sample exercise:Give the complete chemical symbol for the nuclide that contains 18 protons, 18 electrons, and 22 neutrons.



5151


Atomic # = 18 , element is Argon



5252


Atomic # = 18 , element is Argon

40Ar


18


5353Atomic Theory: IsotopesAtomic Theory: Isotopes

Allotropes - Different chemical forms of the same element existing in the same physical state.

FullereneFullerene GraphiteGraphite

DiamondDiamond


5454

Displays chemical reactivity trends and relationships and constructed to account for (and predict) chemical reactivity of the elements.

For example:

Li, Na, K soft metals, v. reactive w/ water

He, Ne, Ar gases and not reactive

F, Cl, Br reactive with many other elements in a similar fashion

Cu, Ag, Au Metal w/ similar reactivity

Periodic Table; Periodic Table; Dmitri Mendeleev (1869)Dmitri Mendeleev (1869)


5555Periodic Table; Periodic Table; Dmitri MendeleevDmitri Mendeleev


5656Periodic TablePeriodic Table

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1H 2He

3Li 4Be 5B 6C 7N 8O 9F 10Ne

11 Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar

19K 20Ca 21Sc 22Ti 23V 24Cr 25Mn 26Fe 27Co 28Ni 29Cu 30Zn 31Ga 32Ge 33As 34Se 35Br 36Kr

37Rb 38Sr 39Y 40Zr 41Nb 42Mo 43Tc 44Ru 45Rh 46Pd 47Ag 48Cd 49In 50Sn 51Sb 52Te 53I 54Xe

55Cs 56Ba 57La 72Hf 73Ta 74W 75Re 76Os 77Ir 78Pt 79Au 80Hg 81Tl 82Pb 83Bi 84Po 85At 86Rn

87Fr 88Ra 89Ac 104Unq 105Unp 106Unh 107Ns 108Hs 109Mt

58Ce 59Pr 60Nd 61Pm 62Sm 63Eu 64Gd 65Tb 66Dy 67Ho 68Er 69Tm 70Yb 71Lu

90Th 91Pa 92U 93Np 94Pu 95Am 96Cm 97Bk 98Cf 99Es 100Fm 101Md 102No 103Lr

GroupGroupor Familyor Family

RowRow

11 Alkali metalsAlkali metals Li, Na, K,...Li, Na, K,...22 Alkaline earth metalsAlkaline earth metals Be, Mg, Ca,...Be, Mg, Ca,...1616 Chalcogens (chalk formers)Chalcogens (chalk formers) O, S, Se,...O, S, Se,...1717 Halogens (salt formers)Halogens (salt formers) F, Cl, Br,...F, Cl, Br,...1818 Noble Gases (inert gases)Noble Gases (inert gases) He, Ne, Ar,...He, Ne, Ar,...


5757Periodic TablePeriodic Table

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1H 2He


11 Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar







alkali metalsalkali metals

alkaline earth metalsalkaline earth metals

metalsmetals

metalloidsmetalloidsnon-metalsnon-metals

noble gasesnoble gases

rare earthrare earth metalsmetals


5858

metalsmetals non-metalsnon-metalsconductors insulators

shiny dull

high thermal conductivity thermal insulators

solids at RT freq. non-solids at RT

ductile brittle

Periodic Table (1869)Periodic Table (1869)

Metalloids (along line in table) have properties between metals and non-metals


5959

Molecule Molecule - “assembly” of two or more atoms (with - “assembly” of two or more atoms (with properties different from constituent types of atoms (see properties different from constituent types of atoms (see ““Law of Multiple ProportionsLaw of Multiple Proportions”). i.e., H”). i.e., H22O, HO, H22OO22, CaCO, CaCO33, , HNOHNO33, H, H22SOSO44,...,...

some elements found in nature as molecules (i.e., some elements found in nature as molecules (i.e., OO22, N, N22, etc... [diatomic]), etc... [diatomic])

FormulasFormulas MolecularMolecular - actual numbers and types of atoms in - actual numbers and types of atoms in

a moleculea molecule EmpiricalEmpirical - smallest whole number ratio of - smallest whole number ratio of

constituentconstituentStructuralStructural - “picture” showing how - “picture” showing how the atoms are attached to one anotherthe atoms are attached to one another

Molecules and IonsMolecules and Ions


6060

Molecular Molecular Empirical Empirical StructuralStructuralFormulaFormula FormulaFormula FormulaFormula

HH22O O (water)(water) HH22OO

HH22OO22 (hydr. peroxide)(hydr. peroxide) HOHO

CC22HH44 (ethylene)(ethylene) CHCH22

CC66HH1212OO6 6 (glucose)(glucose) CHCH22OO

O

H H

H O

OH

H

OH

H

OHH

OH

CH2OH

H

H

O O

H

C C

H

H

H

H

Molecules Molecules


6161FormulasFormulas

Ethylene is a gas at room temperature and is the Ethylene is a gas at room temperature and is the starting material for for many plastics. Its starting material for for many plastics. Its molecular formula is Cmolecular formula is C22HH44.

– What is its empirical formula?

– What other molecular formulas are possible for this same empirical formula?



Ethylene is a gas at room temperature and is the Ethylene is a gas at room temperature and is the starting material for for many plastics. Its starting material for for many plastics. Its molecular formula is Cmolecular formula is C22HH44.


CHCH22

– What other molecular formulas are possible for this same empirical formula?

CC22HH4 4 , C, C33HH6 6 , C, C44HH8 8 ,,

CC55HH10 10 , ..., ...



Cucurbituril is a compound with cage-like Cucurbituril is a compound with cage-like molecules big enough to surround and loosely trap molecules big enough to surround and loosely trap smaller molecules. It has the molecular formula smaller molecules. It has the molecular formula CC3636HH3636NN2424OO1212.




Cucurbituril is a compound with cage-like Cucurbituril is a compound with cage-like molecules big enough to surround and loosely trap molecules big enough to surround and loosely trap smaller molecules. It has the molecular formula smaller molecules. It has the molecular formula CC3636HH3636NN2424OO1212.


CC33HH33NN22OO



Sample exercise: Give the empirical Sample exercise: Give the empirical formula for the substance whose formula for the substance whose molecular formula is Simolecular formula is Si22HH66..



Sample exercise: Give the empirical Sample exercise: Give the empirical formula for the substance whose formula for the substance whose molecular formula is Simolecular formula is Si22HH66..

SiHSiH33


6767

atoms can gain or lose electrons to become charged (called ions)

positive ion = cationnegative ion = anion

Na (neutral has 11 electrons) can easily lose 1 electron to become a cation (Na+1)

Ions Ions


6868

Polyatomic ions; molecules with charges. i.e., NO3

-1, SO4

-2, PO4-3, etc...

chemical properties of ions may be VERY different from similar neutral species

Predicting charges on ions - use periodic table (gain or lose electrons to end up with the same number as the nearest noble gas)

Ions Ions


6969

+1 +2+1 +2 -3 -2 -1 -3 -2 -1

Ions Ions 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

1H 2He


11Na 12Mg 13Al 14Si 15P 16S 17Cl 18Ar








7070

Sample exercise: How many protons and electrons does the Se2- ion possess?

Ions Ions


7171

Sample exercise: How many protons and electrons does the Se2- ion possess?

Se atomic number = 34

# of protons = 34

# of electrons = 34 + 2 = 36

Ions Ions


7272

transfer of electrons between atoms, Na + Cl = [Na]+[Cl]-

ionic compounds contain anions and cations, typically combinations of metals and non-metals (molecular compounds, in which electrons are shared, are usually result from the combination of non-metals only); FeS, LiBr, CuSO4, TiO4, etc...

total charge is neutral; total (+) = total (-) ionic compounds are arranged in a 3D array (packing of

ping-pong balls) usually only empirical formulas can be written for ionic

compounds (because no real molecular unit in solid phase but “extended” lattice)

usually solids but soluble in water insol. in organic sols.

Ionic Compounds Ionic Compounds


7373

Cation Anion Charges Empirical Formula

sodium (Na) chlorine (Cl) Na+1 + Cl-1 NaClmagnesium(Mg) nitrogen (N) Mg+2 + N-3 Mg3N2

aluminum (Al) bromine (Br) Al+3 + Br-1 AlBr3

barium (Ba) sulfate (SO4) Ba+2 + SO4-2 BaSO4

lithium (Li) carbonate (CO3) Li+1 + CO3-2 Li2CO3

nickel (Ni) chloride (Cl) Ni+2 + Cl-1 NiCl2

Ni+3 + Cl-1 NiCl3

total charge is neutral; total (+) = total (-)



7474

+-

-

-

-

-

-

-

-

++

+

+

+

++

-

-

+

+ +-

+

-+-

-


- -

- -

-

+

+ +

+

Unit Cell Unit Cell

Cell FaceCell Face


7575

Sample exercise: Which of the following compounds are molecular?

CI4

FeS

P4O6

PbF2



7676

Sample exercise: Which of the following compounds are molecular?

CI4

FeS

P4O6

PbF2



7777

Sample exercise: Write the empirical formulas for the compounds formed by the following ions:

a) Na+ and PO43-



7878


b) Zn2+ and SO42-



7979


c) Fe3+ and CO32-



8080

Method for unambiguously referring to the a. 15 million known molecules)

Organic compounds - containing C combined typically with H, O, N, and S (originally associated with living organisms but no longer relevant definition)

Inorganic compounds - all other compounds

Nomenclature:Nomenclature: naming inorganic compounds naming inorganic compounds


8181

Traditional names for compounds long known (ammonia [NH3], water [H2O], Zeise’s salt [Pt(C2H4)Cl3]-1], Muriatic Acid [HCl], etc...)

common names (somewhat systematic, ferrous chloride, cupric chloride, etc...)

International Union of Pure and Applied Chemistry rules (IUPAC)

Nomenclature:Nomenclature: naming inorganic compounds naming inorganic compounds


8282

Ionic compounds are names based upon the component ions.Ionic compounds are names based upon the component ions. Positive ion (cation) named and written firstPositive ion (cation) named and written first Negative ion (anion) named and written lastNegative ion (anion) named and written last Solve ambiguity in charge by using Roman numeralsSolve ambiguity in charge by using Roman numerals

Nomenclature:Nomenclature: naming ionic compoundsnaming ionic compounds

CationCation AnionAnion CompoundCompound NameNameNaNa++ ClCl- NaClNaCl sodium sodium chloridechlorideAlAl+3+3 OO-2-2 AlAl22OO33 aluminum aluminum

oxideoxideFeFe+2+2 OO-2-2 FeOFeO iron(II) oxideiron(II) oxide

(ferr(ferrousous oxide) oxide)

FeFe+3+3 OO-2-2 FeFe22OO33 iron(III) iron(III)

oxideoxide (ferr(ferricic oxide) oxide)


8383

Monoatomic - take the name from the element» Li+1 lithium ion Sr+3 strontium ion

» Ca+2 calcium ion

Polyatomic - only one common polyatomic cation » NH4

+1 ammonium ion

Multiple Cationic Charge Possible - specify charge with Roman numerals to be unambiguous

» Fe+2 iron(II) ion Fe+3 iron(III) ion

» Cr+6 chromium(VI) ion Cr+5 chromium(V) ion

For metals, older method used to distinguish between ions differing by one charge unit by adding suffix (-ous for lower charge, -ic for higher charge)

» Fe+2 ferrous ion Fe+3 ferric ion

» Co+2 cobaltous ion Co+3 cobaltic ion

Nomenclature:Nomenclature: naming cationsnaming cations


8484Nomenclature:Nomenclature: naming anionsnaming anions Monoatomic - add -ide suffix

» F-1 fluoride ion P-3 phosphide ion

» O-2 oxide ion B-5 boride ion

Polyatomic - some common use -ide suffix » OH-1 hydroxide ion CN-1 cyanide ion

» N3-1 azide ion O2-2 peroxide ion

Oxyanions - (1) when only two, the one with less oxygen ends in -ite and the one with more oxygen ends with -ate

» NO2-1 nitrite ion NO3

-1 nitrate ion

» SO3-2 sulfite ion SO4

-2 sulfate ion

Oxyanions- for species with more than two members use prefixes (hypo- less oxygen and per- more oxygen)ClO-1 ClO2

-1 ClO3-1 ClO4

-1 hypochlorite chlorite chlorate perchlorate


8585

Acid - compound which yields H+ when dissolved in water write hydrogen first; HCl, H2SO4, H3PO4, etc... anions which end in -ide use hydro- as prefix and -ic as

suffix

Nomenclature:Nomenclature: acidsacids

Anion AcidCl- (chloride) HCl (hydrochloric acid)F- (fluoride) HF (hydrofluoric acid)

oxyacids - replace -ate suffix of anion with -ic,

replace -ite suffix of anion with -ous (leave prefixes!)

Anion AcidClO2

- (chlorite) HClO2 (chlorous acid)ClO3

- (chlorate) HClO3 (chloric acid)ClO4

-1 (perchloric) HClO4 (perchloric acid)


8686

Similar to ionic compounds

– More positive element (left and down on periodic table) named first (first in formula also)

– Second element name ends with -ide

– Use numbering prefixes if necessary

Nomenclature:Nomenclature: molecular compoundsmolecular compounds

PrefixPrefix NumberNumberMono- 1Di- 2Tri- 3Tetra- 4Penta- 5Hexa- 6Hepta- 7Octa- 8Nona- 9Deca- 10

FormulaFormula NameName (text prob. 2.45)N2O5 dinitrogen pentoxideIF7 iodine heptafluorideXeO3 xeon trioxideSiCl4 silicon tetrachlorideH2Se dihydrogen selenideP4O6 tetraphosphorus hexoxide


8787

zinc(II) chloride ammonium sulfate iron(III) fluoride hydrobromic acid perbromic acid sulfur hexafluoride hydrogen cyanide

Nomenclature:Nomenclature: examplesexamples

FormulaFormula NameName ZnCl2

(NH4)2SO4

FeF3

HBr

HBrO4

SF6

HCN


8888

Atomic Theory Experiments leading to the discovery of atomic

structure The Periodic Table Molecules and Ions Nomenclature

End Chapter 2End Chapter 2

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Chapter 2: Atoms, Molecules and Ions