review of atomic theory

QuickTime™ and a decompressor

are needed to see this picture.

Period 7.

•Pre-Socratic philosopher

•Born in Abdera, Elea, or Miletus in the 5th

Century B.C.



• Lived from 460-370 B.C

• Ancient Greek philosopher

• His mentor was Leucippus

• The two of them worked together on atoms

•He was more of a scientists than other Greek philosophers

•Leucippus and Democritus realized that the world consisted of myriads of indivisible particles, called atoms which were the smallest particles of matter possible

•Upon further speculation, they came up with the idea that the observable properties

of common materials are because of the different shapes of atoms which they contain, or different motions of atoms

• Lived from 384 to 322 BC

• He was a Greek philosopher

• A student of Plato and a teacher of Alexander the Great

• Had ideas referring to many different subjects



• Aristotle’s Theory of the Elements: A piece of matter could be divided an infinite number of times and one would never

find a piece of matter that could be further divided

• He believed in the four elements: earth, fire, water, and air

• According to him, everything in the world was made up of some combination of these four elements

•At this time this was the most popular theory.

•The atomic theories that were created at this time were not 100% accurate; however, they provided insight in an

area never explored before•The central ideas of Leucippus and

Democritus have remained unchanged

Antoine Lavoisier & The Law of Conservation of Matter

By: Jin Shin & Taylor Seeman

Born: August 26, 1743

Died: May 8, 1794

“Father of Modern Chemistry”

• Attended the College Mazarin at the request of his aunt

• College Mazarin had an excellent mathematics and science program

• Lavoisier was a brilliant student, and earned numerous awards

• He conducted his first few experiments individually or while aiding professors.

Educational Background

Experiment

• Lavoisier burnt phosphorous and sulfur in air and proved the products weighed more than the reactants but the weight gained was lost from the air.

Experiment

• When you heat a piece of copper metal in air, it comes together with oxygen in the air. If you weigh it, it is found to have a greater mass that the original piece. However, the mass of the oxygen of the air is combined with the mass of copper, the mass of the product is equal to the sum of the masses of the copper and oxygen that were combined.

Significance of Concept

• Showed that the quantity of matter is the same in the beginning and end of every chemical reaction, though matter may change its state.

• Though matter may change form, it can neither be created nor destroyed

• Mass of reactants always equal the mass of products

Significance of Concept

• Law demonstrates understanding of the properties of movement and energy.

• It is a fundamental principle of physics.

• Sources:• http://www.iscid.

org/encyclopedia/Law_of_Conservation_of_Mass

• http://www.biographybase.com/biography/Lavoisier_Antoine_Laurent.html

http://www.iscid.org/encyclopedia/Law_of_Conservation_of_Mass





http://www.biographybase.com/biography/Lavoisier_Antoine_Laurent.html






Joseph Proust: Law of Definite Proportions

By: Simir and Katie



-born in France (1754-1826)

-son of a pharmacist

-chief apothecary at Saltpetriere Hospital

-became the director of Royal Laboratory under Charles IV

-laboratory was destroyed by the invasion of Spanish Army by Napoleon so he returned to France

Joseph Proust

-Lived in poverty before being awarded pension by Louis XVIII

-He taught at the Chemistry school at Segovia and the University of Salamanca at Spain

-He was the chair of this school and was proposed in 1784 to to train artillery cadets with the latest scientific knowledge

-He worked with Antoine Lavosier

-He also taught chemistry at Musee, a private school in Paris,



Experiment

• Proust prepared a copper carbonate compound

• He heated it, getting rid of the water and then the carbonic acid, or what was left of the copper oxide

• - From the 180 lbs of "copper carbonate" (it was actually carbon dioxide) he took away 10 lbs of water and 46 of the carbon dioxide

• - The copper oxide left had 100 lbs of copper and 25 of oxygen

Experiment

• Decomposition of CuCO3 into Cu, C and O

• Proust found that the ratio of the masses of Cu to C to O was always the same no matter what size sample of CuCO3 he started with.

• He formed his theory by dividing to find the ratios







Example Set of Data

Significance

• Law of Definite Proportions• Copper carbonate must always be made

from the same fixed proportions of copper, carbon, and oxygen

• All compounds contain elements in certain definite proportions

• Ex) Nitric Oxide- 8:7 oxygen to nitrogen• Ex2) Water- 8:1 oxygen to hydrogen

Significance in the Scientific Community

• Initially not accepted by all chemists• ie) Claude-Louis Berthollet

argued that elements could combine in many different proportions (actually thinking of solutions/mixtures- Proust was thinking of compounds)

• Law of Definite Proportions was the basis for John Dalton’s atomic theory and multiple proportions





Significance in Scientific Community cont

Proust expanded upon Lavoisier’s Law of Conservation of Mass

Law of Conservation of Mass-mass of reactants was always equal to mass of products (matter cannot be created or destroyed)

Proust measured each individual substance instead of the total mass for reactants and products



John Dalton Early Life

• From Cumberland, England • Birth date is unknown • Family were Quakers• Worked in the fields and in

the family cloth shop• Relatively poor• Did not get formal education

– Did get basic lessons in reading, writing, and arithmetic

John Dalton Adult Life

• Dalton and his brother ran a school in Kendal

• Dalton recorded the weather patterns each day (for his entire life) in a journal

• Originally wanted to be a physician, decided on scientist instead

• Tutored students at Manchester University

Dalton’s Law of Multiple Proportions

If 2 elements formmultiple compounds,the ratios of themasses of the secondelement combiningwith a fixed mass ofthe first element willbe in ratios of smallwhole numbers

If 2 elements formmultiple compounds,the ratios of themasses of the secondelement combiningwith a fixed mass ofthe first element willbe in ratios of smallwhole numbers

Dalton’s Law of Multiple Proportions

For Example Elements Y and Z

The weight of Element Z, when combined with the fixed weight of element Y, will compute to a ratio of small integral numbers (2:1, 3:1, etc.)

OR

Carbon + Oxygen = CO, CO2, but not CO1.3

For Example Elements Y and Z

The weight of Element Z, when combined with the fixed weight of element Y, will compute to a ratio of small integral numbers (2:1, 3:1, etc.)

OR

Carbon + Oxygen = CO, CO2, but not CO1.3

Importance of Dalton’s Law of Multiple Proportions

• One of the fundamental laws of stoichiometry

• Basis for other Atomic Theories– Law of Conservation

of Mass– Law of Definite

Proportions

Dalton’s Modern Atomic Theory

• All matter is made of atoms• Atoms are invisible and

indestructible • All atoms of a given element

are identical in mass and properties

• Compounds are formed by a combinations of two or more different kinds of atoms

• A chemical reaction is a

rearrangement of atoms

The Discovery

• Dalton studied gases– Discovered the partial

pressures of gases • Lead to formulation of working

theory of the atom • *Noticed that certain gases

maintained the same ratios of mixture regardless of amount

• Realized that Ratios remain the same because they were consistent down to the smallest particle or atom

Significance of Dalton’s Atomic Theory

• First understanding of the atom– Prior to, it was an

abstract philosophical concept

• The essence of Dalton’s theory remains valid

• Led to great expansion of theoretical thought in chemistry

JJ Thomson

-Discovered the electron and also invented the mass spectrometer

-Interested in sciences as a child and later on his life showed a large interest in atomic structure

-Graduated and taught at Trinity College after a brief stay at Owens College

-Was an author of many non-fiction science books



Personal Life

-Born in Cheetham Hill, Manchester on Decemeber 18, 1856

-Full name Sir Joseph John Thomson

-Father died when he was only 16

-In 1890 he married Rose Elizabeth

-He had one son named Sir George Paget Thomson



The Discovery

-A century ago discovered the electron while using a Cathode Ray Tube

-Cathode Ray Tube is a glass tube that has wiring attached to its two sides.

-The air is taken out and in order to try and form a vacuum.

-An electric charge goes from one end to the other and produces a glow that looks fluorescent.

-A cathode ray or electron gun is attached to the glass contraption



The Experiment

-Used his Cathode Ray Tube made a unique tube to probe that the rays shot in had a negative charge.

-Almost perfect vacuum and he put the fluorescent layer on a specific side.

- Had an electric plate, this gave a positive charged electrode to the negative cathode. The ray would be deflected.

-Shot a ray got deflected by the opposite positive charge. This showed that the ray was made up of charged, negatively particles.



The Third Experiment

-Figured out that the charge to mass ratio could have been very large or extremely small

-Chose correctly that they were very small



Significance

-Later Devices, helps with electronic devices, making impulses so a screen can run and one can see a display.

-Cathode-Ray Tube can produce an image on a screen with electrical impulses.

-It can primarily help with TV screens and computer screens.

-Disproved Plum-Pudding theory



Robert Andrews Millikan

-born in 1868 in Illinois

-grew up in Iowa

-worked on Oil Drop Experiment in University of Chicago (professor)

-1923: Nobel Prize for Physics



The Discovery

• At University of Chicago

• Performed a series of experiments

• Wanted to find the charge of an election

• Worked off Thomson’s experiments



The Experiment

• The atomizer produces fine oil droplets• Oil droplets fall through a hole in the first chamber as

a stream of tiny droplets• X-rays negatively charge the oil droplets• An applied voltage on two plates surrounding the oil

drops creates an electric field. The electric force pull some drop upward.

• The rate at which the oil droplets are falling and rising between the two charged plates is measured through the microscope.

The Experiment• Some oil droplets fell, and some did not• This depended on the forces acting upon it: electric force, gravitational

force, and air resistance• He found…• 1. When a large electric field is applied, but the electric force on the

droplet is larger, then the gravitation force acts in the opposite direction: it moves upward

• 2. Net force of a droplet=sum of the gravitational force, the air resistance, and electrical force

• V1=k(Eq-mq)



The Experiment

• In simpler terms…• When there was no voltage applied, the droplet would

fall down to the bottom• Voltage applied, droplets with negative charge drop

more slowly, stop altogether, or even go up (depending on the voltage given)

• Charges of the droplets were all multiples of the smallest value

• e-=1.6 x 10 to the -19 coulombs

Significance of Experiment

• Calculated charge of electron

• Showed that charge on electron was smallest possible amount of charge

• Total amount of electric charge must always be an integer multiple of this electric charge



Significance of Experiment

• Now that the charge of an electron is discovered, further advancements in science can be made on the atom

• An atom is the basic unit of an element• With the discovery of an electron, we can find

out more on the states of substances, elements, etc.

• Without him, chemistry would not have advanced much

Earnest Rutherford

As well as Marsden and Geiger and their gold foil experiment



Background Info

• Ernest Rutherford, 1st Baron Rutherford of Nelson was a British-New Zealand chemist and physicist. In his early work he discovered the concept of radioactive half and also differentiated and named alpha and beta radiation. He was awarded the Nobel Prize in Chemistry in 1908 "for his investigations into the disintegration of the elements, and the chemistry of radioactive substances”.

Before his Experiment

Before his experiment people though that the particles in an atom were randomly arranged according to the plum pudding model. See diagram below.

Hypothesis

Rutherford thought that if the plum pudding model was correct then a beam of alpha particles would go though matter with very little deflection. See diagram below.

ExperimentRutherford’s experiment consisted of a block of radium to

generate alpha particles, gold foil for the particles to pass trough and a florescent screen that he could use to determine where the alpha particles ended up. See diagram below.

Conclusions

The Gold Foil experiment showed that the plum pudding model of the atom was not accurate. This is because the experiment showed how there had to be a piece of the atom with a large mass in the center of the atom. The realization that things were not just loosely "hanging out" around an atom but instead are arranged in a specific way around a center led him to discover the Atomic Nucleus. See diagram below

More Conclusions

Without this discovery, much of what we know about atoms would not be possible. If not for the discovery of the nucleus, we could not know about the important parts that it consists of (protons and neutrons). Also, the periodic table of elements that we all know so well (from intense memorization for Chemistry tests), the elements would not be ordered the same way, because Atomic number is the number of protons in the nucleus of an atom. Also, we can also identify different atoms by mass number. This is the number of protons and neutrons added together in the nucleus. All these things, and many more, that are the basis of our knowledge of atoms would not be possible without the information from Rutherford's Gold Foil Experiment.

James Chadwick Background Info

•Chadwick was born in Cheshire, England in 1891.•He went to Manchester University in 1908.•After college, he spent his time studying under Professor Rutherford.•Professor Rutherford created the first artificial nuclear transformation.•This is where he made studies on atomic nuclei.•In 1921, he became Assistant Director of Research of the Cavendish Laboratory.•In 1927, he was elected a Fellow of the Royal Society.

Background Info (con’t) In 1932, he discovered the

existence of neutrons. For this he was awarded the

Hughes Medal of the royal society.

He was later awarded the Nobel Peace Prize in 1935 for physics.

From 1943 to 1946, he worked in the United States on the Manhattan Project for the development of the atomic bomb.

He retired in England in 1948. He died in 1974.

• http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html

http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html




Neutron Discovery

Rutherford discovered the proton in the nucleus Noticed it was not the only particle in the nucleus Atomic mass could not only be the mass of protons (e.g. Helium has an

atomic mass of 4, but the number of protons is 2 Chadwick went further in trying to discover the neutron, and kept on trying, even as he

failed. Walter Bothe and Herbert Becker did experiments with beryllium where it emitted radiation

to penetrate 200 mLs of lead. They thought this was high energy gamma rays, but Chadwick noticed it was something else

Without the clues and inspirations of Rutherford, Bothe, and Becker, Chadwick would not have been able to discover the neutron.

Neutron Discovery (Cont.) Two other scientists, Federic and Irlene Joliot-Curry, tracked particle radiation by putting

paraffin wax in front of the rays (thought to be gamma rays) coming from the beryllium. During this, they observed high-speed protons coming out the paraffin.

Chadwick recognized the rays from the beryllium were not gamma rays because they were too strong. He concluded that they were neutrons. He did his own experiments to back this up.

Since neutrons are neutral, they can penetrate thick layers of different substances because they are not disturbed by positive or negative charges.

Chadwick also discovered that the mass of a neutron is 1.0067

http://www.helium.com/items/216709-james-chadwick-and-his-discovery-of-the-neutron

The Neutron Experiment

Significance By knowing about the neutron,

scientists could use atomic number and atomic mass because they were no longer extremely similar.

Also, knowing about neutrons was important in the creation of nuclear weapons and nuclear reactors.

In addition, the creation of plutonium-235 and uranium-235 is caused by their absorption of neutrons.

Significance (Cont.) At extremely high pressure and temperature, neutrons and electrons collapse

into neutronic matter, known as neutronium. This is what happens in neutron stars

Neutron capture results in neutron activation, which creates radioactivity Used to excited delayed and prompy gamma rays from elements in materials Neutron emitters can detect light in the nuclei, especially hydrogen found in

water molecules.

http://en.wikipedia.org/wiki/Neutron

Niels Bohr

Born: Copenhagen, Denmark, in 1885

Died: Copenhagen, Denmark, in 1962 of

heart failure

A Doctor of Physics

Background Info.

• Awarded Nobel Prize for his work in the structure of atoms in 1922

• Worked under J.J. Thomson in Cambridge, and later with Ernest Rutherford in Manchester University, in the field of physics

The Bohr Model

• Developed model of atom in which electrons orbited the nucleus in certain energy levels. Called the Bohr Model.

• Conducted the Liquid Drop Experiment.

The Shell Model

• Developed Shell Model in which the outermost orbit of electrons determined the chemical properties of the element.

Niels Bohr

The fact that electrons can only absorb or emit energy in chunks, or quanta, laid the foundation for theorizing just how electrons are arranged in an atom. This and the explanation of another puzzling phenomena lead Niels Bohr to propose the first model of the atom that provided the first illustration the arrangement of electrons in an atom.

Line Spectra

Early in the century it was observed that samples of elements emit light when they are vaporized in an intense flame.

The light that is seen results from the atoms of the element absorbing the energy of the flame and releasing the absorbed energy in the form of light.

When this light is passed through a prism, a resulting line spectra of specific wavelengths results. This line spectra is unique for each element.

Line Spectra

Courtesy of: http://upload.wikimedia.org/wikipedia/commons/thumb/e/e5/Flametest--Na.swn.jpg/200px-Flametest--Na.swn.jpg

Courtesy of: ://www.luc.edu/faculty/spavko1/JCE/line-spectra/SODIUM.GIF http

Notice that the color flame produced from the vaporization of sodium is yellow. If the yellow light is separated into its component wavelengths with a prism, the resulting spectrum is shown at left.

Niels Bohr Conn…

Bohr was the first to see the connection between the characteristic line spectra of each element and atomic structure.

Using Rutherford’s nuclear atom and Plank’s idea of quantization, Bohr created a model of the atom that explained line spectra.

His model of the atom still represents the simplified atom today.

The Bohr Model of the Atom

Bohr proposed that the electrons of an atom must be arranged in certain orbits that correspond to the amount of energy of that electron (these energies are represented by the letter “n” and increase as the distance from the nucleus increases.) Here, Hydrogen is represented, since on proton is present and one electron orbits the nucleus.

Courtesy of: http://upload.wikimedia.org/wikipedia/commons/9/9b/Bohratommodel.png

How does this Explain Line Spectra?When an electron absorbs a photon with high enough energy, it becomes excited and jumps to the energy level that corresponds to the new energy of the electron. When the electron releases the absorbed energy and returns to its original position, light is released. Because the energy levels of the electrons are quantized, only certain photons will allow the electron to absorb enough energy to jump to n=2, n=3 and so on. Therefore, only certain wavelengths will be released upon return to the original energy level.

Although Bohr’s model worked well for the hydrogen atom, it could not Although Bohr’s model worked well for the hydrogen atom, it could not explain spectra of elements with more than one electron.explain spectra of elements with more than one electron.

The Wave Nature of LightThe Wave Nature of Light

Significance of Bohr and Shell Model

• Shell Model is used as a basis for Chemistry, since Chemistry is about the RXNS and interactions between elements/chemicals

• The Bohr Model gave a more accurate model of an atom. The fact that electron movement was not applicable in classical mechanics caused the introduction of quantum mechanics into modern science.

Contributions, cont.• Helped develop the Atomic Bomb

(part of Manhattan Project/Atomic Energy Project)

• Began work in Theoretical Quantum Physics (Old Quantum Physics)

• Identified isotope of Uranium responsible for slow-neutron fission

Heisenberg realised that

• In the world of very small particles, one cannot measure any

property of a particle without interacting with it in some way

• This introduces an unavoidable uncertainty into the result

• One can never measure all the

properties exactly

Werner Heisenberg (1901-1976)

The Atom

Atomic Number and Mass Number

Isotopes

Atomic Theory

Atoms are building blocks of elements

Similar atoms in each element

Different from atoms of other elements

Two or more different atoms bond in simple ratios to

form compounds

Subatomic Particles

Particle Symbol Charge RelativeMass

Electron e- 1- 0

Proton p+ + 1

Neutron n 0 1

Location of Subatomic Particles

10-13 cm

electrons

protons

neutrons

10-8 cm

nucleus

Atomic Number

Counts the number

of

protons

in an atom

Atomic Number on the Periodic Table

11

Na

Atomic Number

Symbol

All atoms of an element have the same number of protons

11

Na

11 protons

Sodium

Learning Check AT 1

State the number of protons for atoms of each of the following:

A. Nitrogen

1) 5 protons 2) 7 protons 3) 14 protons

B. Sulfur


C. Barium


Solution AT 1

State the number of protons for atoms of each of the following:

A. Nitrogen

2) 7 protons

B. Sulfur

2) 16 protons

C. Barium

3) 56 protons

Number of Electrons

An atom is neutral The net charge is zeroNumber of protons = Number of electronsAtomic number = Number of electrons

Mass Number

Counts the number

of

protons and neutrons

in an atom

Atomic Symbols

Show the mass number and atomic number

Give the symbol of the element

mass number

23 Na sodium-23

atomic number 11

More Atomic Symbols

16 31 65

O P Zn

8 15 30

8 p+ 15 p+ 30 p+

8 n 16 n 35 n8 e- 15 e- 30 e-

Isotopes

Atoms with the same number of protons,

but different numbers of neutrons.

Atoms of the same element (same atomic

number) with different mass numbers

Isotopes of chlorine

35Cl 37Cl17 17

chlorine - 35 chlorine - 37

Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.

12C 13C 14C 6 6 6

#P _______ _______ _______

#N _______ _______ _______

#E _______ _______ _______

An atom of zinc has a mass number of 65.

A. Number of protons in the zinc atom

1) 30 2) 35 3) 65

B. Number of neutrons in the zinc atom

1) 30 2) 35 3) 65

C. What is the mass number of a zinc isotope

with 37 neutrons?

1) 37 2) 65 3) 67

Write the atomic symbols for atoms with the following:

A. 8 p+, 8 n, 8 e- ___________

B. 17p+, 20n, 17e- ___________

C. 47p+, 60 n, 47 e- ___________

An atom has 14 protons and 20 neutrons.A. Its atomic number is

1) 14 2) 16 3) 34

B. Its mass number is1) 14 2) 16 3) 34

C. The element is1) Si 2) Ca 3) Se

D. Another isotope of this element is

1) 34X 2) 34X 3) 36X 16 14 14

Masses of Atoms

A scale designed for atoms gives their small atomic

masses in atomic mass units (amu)

An atom of 12C was assigned an exact mass of 12.00

amu

Relative masses of all other atoms was determined by

comparing each to the mass of 12C

An atom twice as heavy has a mass of 24.00 amu. An

atom half as heavy is 6.00 amu.

Atomic Mass

Listed on the periodic table

Gives the mass of “average” atom of each element compared to 12C

Average atom based on all the isotopes and their abundance %

Atomic mass is not a whole number

Na22.99

Using the periodic table, specify the atomic mass of each element (round to the tenths place):

A. calcium __________

B. aluminum __________

C. lead __________

D. barium __________

E. iron __________

Calculating Atomic Mass

Percent(%) abundance of isotopes

Mass of each isotope of that element

Weighted average =

mass isotope1(%) + mass isotope2(%) + …

100 100

Atomic Mass of Magnesium

Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70%

25Mg = 25.0 amu 10.13%

26Mg = 26.0 amu 11.17%

Atomic mass (average mass) Mg = 24.3 amu

Mg24.3

Gallium is a metallic element found in small

lasers used in compact disc players. In a sample

of gallium, there is 60.2% of gallium-69 (68.9 amu)

atoms and 39.8% of gallium-71 (70.9 amu) atoms.

What is the atomic mass of gallium?

Ga-69

68.9 amu x 60.2 = 41.5 amu for 69Ga

100

Ga-71 (%/100)

70.9 amu x 39.8 = 28.2 amu for 71Ga

100

Atomic mass Ga = 69.7 amu

Finding An Isotopic Mass

A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope?

Assign X and Y values:X = % 10B Y = % 11B

Determine Y in terms of XX + Y = 100Y = 100 - X

Solve for X:X (10.0) + (100 - X )(11.0) = 10.8

100 100

Multiply through by 10010.0 X + 1100 - 11.0X = 1080

Collect X terms

10.0 X - 11.0 X = 1080 - 1100

- 1.0 X = -20

X = -20 = 20 % 10B

- 1.0

Y = 100 - X

% 11B = 100 - 20% = 80% 11B

Copper has two isotopes 63Cu (62.9 amu) and 65Cu (64.9 amu). What is the % abundance of each isotope? (Hint: Check periodic table for atomic mass)

1) 30% 2) 70% 3) 100%

2) 70%

Solution

62.9X + 6490 = 64.9X = 6350

-2.0 X = -140

X = 70%