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Chapter 3 Atomic Structure. You will explain why the model of the atom changed throughout history. Objective:. What is a model?. Models are used to help us understand things that cannot be seen directly

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Chapter 3 atomic structure

Chapter 3Atomic Structure



What is a model
What is a model? throughout history.

  • Models are used to help us understand things that cannot be seen directly

  • Models are used when something is too large, too small, or too dangerous to be studied directly.


Examples of scientific models
Examples of Scientific Models throughout history.

This model shows the alignment between the sun, moon, & earth. As it rotates, it shows the phases of the moon and how we measure a year.

This model is a mathematical representation of a sound wave. You cannot see sound, but you can see how it affects other objects with its vibrations.


Examples of scientific models1
Examples of Scientific Models throughout history.

  • What other examples can you think of?

  • Are there other models present in this room?


A good model
A good model… throughout history.

  • Must be based on observations and indirect experimentation.

  • Must explain as many characteristics of the original object as possible.

  • Should be as simple as possible.


When do you change a model
When do you change a model? throughout history.

  • All models have limitations —No model has ever been totally complete.

  • A model changes when observations of a new situation do not agree with the current model.


Creating a model
Creating a Model throughout history.

  • The “Think Tube”is also a model for something you cannot see directly.

?

THINK TUBE


Creating a model1
Creating a Model throughout history.

  • How many strings are on the inside?

  • Make your own model showing how

    the “Think Tube” works.


Atoms
Atoms throughout history.

  • The atom has not changed over time, but our idea and model of the atom has.


Definition of atom
Definition of Atom: throughout history.

  • the smallest particle of an element that retains the chemical properties of that element.


Democritus 400 bc
Democritus 400 BC throughout history.

By convention there is color,By convention sweetness,By convention bitterness,But in reality there are atoms and space.   -Democritus (c. 400 BCE)

Convention means because we said so- doesn’t really exist


Democritus 400 bc1
Democritus 400 BC throughout history.

  • Democritus was smashing up sea shells one day and thought that you can break down the shell to tiny pieces, but it can not be completely destroyed.


Democritus 400 BC throughout history.

  • Looked at sand on the beach. Cut sand in half and got fewer and fewer grains of sand.

  • What was the smallest piece?

  • He called it atomos =

    greek word meaning cannot be cut


Democritus 400 bc according to democritus atoms are
Democritus 400 BC throughout history.According to Democritus atoms are:

  • Invisible

  • Indivisible

  • Solid

  • Eternal

  • Surrounded by an empty space

http://www.brl.ntt.co.jp/group/butsuden-g/img/redball.gif


Democritus 400 bc continued
Democritus 400 BC throughout history.continued:

  • Have an infinite number of possible

  • shapes.

  • Each type of atom had a different size.


Democritus 400 bc atoms
Democritus 400 BC throughout history.Atoms -

http://www.brl.ntt.co.jp/group/butsuden-g/img/redball.gif


Aristotle’s Idea 300 BC throughout history.

  • All substances are made of 4 elements: Fire, Air, Earth, and Water


Aristotle s idea 300 bc
Aristotle’s Idea 300 BC throughout history.

  • There were also four qualities: dryness, hotness, coldness, and moistness.

  • Fire was dry and hot, while water was moist and cold, etc.

  • Each of these elements move naturally in a line to their "proper place," where it will be at rest.


Aristotle 300 bc
Aristotle 300 BC throughout history.

  • Water sits on top of the earth, he explained, because it is lighter, yet air floats above the water because it is lighter still—and fire, lightest of all, rises highest. Furthermore, he claimed that the planets beyond Earth were made up of a "fifth element," or quintessence, of which little could be known.


Democritus vs aristotle
Democritus vs Aristotle throughout history.

  • Ancient Greeks accepted Aristotle’s ideas and rejected Democritus.

  • What holds the particles together?

  • Democritus could not answer this question

  • Remained that way until the 17th century


Important Discoveries throughout history.

  • Law of Conservation of Mass

  • Law of Definite Proportions

  • Law of Multiple Proportions


Law of conservation of mass matter
Law of Conservation of Mass (Matter) throughout history.

  • Lavosier measured the mass of chemicals before and after a chemical reaction and found that the weight did not change.

  • In a chemical reaction, matter is neither created nor destroyed.


Law of definite proportions
Law of Definite Proportions throughout history.

  • Also called Law of Constant Composition

  • Proposed by Joseph Proust

  • Elements always react and combine with one another in the same proportions.


Law of definite proportions1
Law of Definite Proportions throughout history.

A chemical compound is always composed of the same combination of atoms -

copper carbonate

CuCO3

http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH02/FG02_01.JPG


Law of definite proportions2
Law of Definite Proportions throughout history.

  • Water has the formula H2O. This means that water in the ocean, lakes, or in our sinks always contains 2 atoms of Hydrogen for every 1 atom of Oxygen. What percent of water is Hydrogen and what percent is Oxygen?

H: 2g/18g = 11% O: 16g/18g = 89%


Law of multiple proportions
Law of Multiple Proportions throughout history.

  • If two elements form more than one compound between them, then the ratios of the weights of the two atoms will be ratios that can be reduced to small whole numbers.

http://cwx.prenhall.com/bookbind/pubbooks/hillchem3/medialib/media_portfolio/text_images/CH02/FG02_02.JPG


Law of multiple proportions1
Law of Multiple Proportions throughout history.


John dalton 1766 1844
John Dalton 1766-1844 throughout history.

  • English school teacher and public lecturer by the age of 12.

  • As a Quaker, Dalton led a modest existence, although he received many honors later in life. In tribute, more than 40,000 people marched in his funeral procession.

http://www.unit5.org/christjs/John_Dalton.htm


John dalton s atomic theory
John Dalton’s Atomic Theory throughout history.

  • Dalton’s Theory was a return to the ideas of Democritus

  • Dalton turned the idea into a scientific theory that could be tested

  • Not all of Daltons ideas are still true today. Some ideas were modified.


John dalton s atomic theory1
John Dalton’s Atomic Theory: throughout history.

  • All matter is composed of atoms.

  • Atoms of a particular element have identical properties. Elements of a different element have different properties.

  • Atoms cannot be divided or destroyed.

  • Atoms combine to form compounds.

  • During a chemical reaction atoms are rearranged.


John dalton s atomic theory2
John Dalton’s Atomic Theory: throughout history.

  • All matter is composed of atoms.

  • Atoms of a particular element have identical properties. Elements of a different element have different properties.

  • Atoms cannot be divided or destroyed.

  • Atoms combine to form compounds.

  • During a chemical reaction atoms are rearranged.


Jj thomson 1856 1940
JJ Thomson 1856-1940 throughout history.

Excuse me... how can you discover a particle so small

that nobody has ever seen one?

http://www.aip.org/history/electron/jjsound.htm


J j thompson s model
J.J. Thompson’s Model throughout history.

_

_

+

+

_

+

+

_

_

+


Discovery of the electron
Discovery of the Electron throughout history.

JJ Thomson determined that:

  • Atom is a sphere of positive matter that holds electrons in it.

  • Also called the plum pudding model or the raisin dough model.


His experiment
His experiment throughout history.

http://www.sciencemuseum.org.uk/on-line/electron/section2/shockwave2.asp


Thomson s experiment

Voltage source throughout history.

Thomson’s Experiment

-

+

Vacuum tube

Metal Disks


Thomson s experiment1

Voltage source throughout history.

Thomson’s Experiment

-

+


Voltage source throughout history.

Thomson’s Experiment

-

+


Voltage source throughout history.

Thomson’s Experiment

-

+


Voltage source throughout history.

Thomson’s Experiment

-

+


Voltage source throughout history.

Thomson’s Experiment

-

+


Voltage source throughout history.

Thomson’s Experiment

-

+


J j thompson s cathode ray tube

Voltage source throughout history.

J.J. Thompson’s Cathode Ray Tube

  • The cathode ray travels from the cathode to the anode when current was passed through the tube.

-

+

Cathode

Anode


Voltage source throughout history.

Thomson’s Experiment

+

-

  • By adding an electric field


Voltage source throughout history.

Thomson’s Experiment

+

-

  • By adding an electric field


Voltage source throughout history.

Thomson’s Experiment

+

-

  • By adding an electric field


Voltage source throughout history.

Thomson’s Experiment

+

-

  • By adding an electric field


Voltage source throughout history.

Thomson’s Experiment

+

-

  • By adding an electric field


Voltage source throughout history.

Thomson’s Experiment

+

-

  • By adding an electric field he found that the moving pieces were negative


Maltese cross tube
Maltese Cross Tube throughout history.

  • Using a Maltese cross as the anode, this produced a shadow that glowed at the end of the tube. This showed that the cathode rays traveled in straight lines.


Paddle wheel discharge tube
Paddle Wheel Discharge Tube throughout history.

  • A paddle wheel placed in the path of the cathode rays turned. This proved that the cathode rays contained mass, and that they might be made of particles.


Thomson s plum pudding model
Thomson's “Plum Pudding Model" throughout history.

http://www.broadeducation.com/htmlDemos/AbsorbChem/HistoryAtom/page.htmt


Thomson s plum pudding model1
Thomson's “Plum Pudding Model" throughout history.

Electrons are red.

Negative electrons

Are embedded in a

Blue positive atom.

http://molaire1.club.fr/e_histoire.html


J j thompson s model1
J.J. Thompson’s Model throughout history.

  • Cathode rays are beams of negatively-charged particles called electrons.

  • All atoms contain electrons.

  • Atoms also contain an equal and opposite positive charge.


Ernest rutherford 1871 1937
Ernest Rutherford 1871-1937 throughout history.

  • "All science is either physics or stamp collecting."

http://www.pbs.org/wgbh/aso/databank/entries/bpruth.html


Ernest rutherford s model
Ernest Rutherford’s Model throughout history.

  • He became a student of a teacher named Professor J J Thomson at Cambridge University in England


Ernest rutherford s model1
Ernest Rutherford’s Model throughout history.

  • Rutherford studied how gold atoms interacted with radioactivity.


Radioactivity
Radioactivity throughout history.

  • Radioactivity is the

    processes by which

    unstable atomsemit

    subatomic particles

    (radiation).


  • Made of throughout history. 2 protons

  • and 2 neutrons.

  • Charge of +2, and a

  • mass of 4

  • Relatively slow and

  • heavy.


  • Charge of throughout history.minus 1

  • Mass is very small.

  • They are the same as

  • an electron.

  • They are fast, and light.


  • Gamma rays are throughout history.

  • waves, not particles.

  • They have no mass

  • and no charge.


Penetrating power
Penetrating Power throughout history.

  • Alpha particles are easy to stop, gamma rays are hard to stop.


Fluorescent throughout history.

Screen

Lead block

Uranium

Gold Foil

Here’s how it looked.


What he expected throughout history.


Rutherford expected
Rutherford Expected: throughout history.

  • The alpha particles to pass through without changing direction.

  • Because…?

  • …the positive charges were thought to be spread out evenly. Alone they were not enough to stop the large alpha particles.


What was expected: throughout history.


What he got throughout history.



What actually happened

+ throughout history.

What Actually Happened…

-

-

-

-

-

-


+ throughout history.

How he explained it:

  • Atom is mostly empty.

  • It has a small

  • dense, positive piece

    at center.

  • Alpha particles are deflected by

    the nucleus if they

    get close enough.

-

-

-

-

-

-


Ernest rutherford s results

+ throughout history.

Ernest Rutherford’s Results:

  • Atom is mostly empty space.

  • Suggests that an atom has a nucleus that holds most of

    the mass of the

    atom.

-

-

-

-

-

-


What actually happened1
What Actually Happened throughout history.


Rutherford s atom a sea of electrons that surrounded a positively charged nucleus
Rutherford’s Atom: throughout history.A sea of electrons that surrounded a positively charged nucleus.


Rutherford s atom
Rutherford’s Atom throughout history.

  • His model of the atom was similar to the solar system. Like planets, electrons orbited a central, sun-like nucleus.

http://www.broadeducation.com/htmlDemos/AbsorbChem/HistoryAtom/page.htmt


Rutherford s atom1
Rutherford’s Atom throughout history.

PROTONS

+


Rutherford s atom2
Rutherford’s Atom throughout history.

1. Most of the mass of an atom must be located in a small volume at the center of the atom (the nucleus).

2. The nucleus is made of positively charged particles called protons.

3. The electrons move in a large volume which is mostly empty space.


Problems with rutherford s atom
Problems with Rutherford’s Atom throughout history.

  • According to "classical" theory the electrons should lose energy by radiating electromagnetic radiation, as they are accelerated electric charges.

  • They should spiral into the nucleus.



2 years after rutherford neils bohr 1885 1962
2 years after Rutherford…. Neils Bohr throughout history. 1885 - 1962


Bohr model of the atom
Bohr Model of the Atom: throughout history.


Bohr model of the atom1
Bohr Model of the Atom: throughout history.

  • Electrons are a particular distance from the nucleus

  • The energy of each electron is not the same

  • Electrons close to center = low Energy

  • Electrons farther away = high Energy


Neils bohr s model
Neils Bohr’s Model throughout history.

  • There are 2 electrons in the lowest energy level, 8 electrons in the second energy level, and 18 in the third…

    …this is the model of the atom we will use!


James chadwick
James Chadwick throughout history.


Chadwick
Chadwick throughout history.

  • In 1932, Chadwick proved the existence of neutrons - elementary particles devoid of any electrical charge.

  • Located in the nucleus

    (Rutherford also put out the idea that there could be a particle with mass but no charge)


Chadwicks atom
Chadwicks Atom throughout history.


Chadwick s atom modern atom
Chadwick’s Atom Modern Atom throughout history.

1. Most of the atom's volume is occupied by electrons.

2. The number and arrangement of electrons in an atom determine its chemical properties.


Chadwick s atom
Chadwick’s Atom throughout history.

3. The identity of an element is determined by the number of protons in the nucleus.

4. Different isotopes of elements exist and differ only in the number of neutrons and hence the mass of the atom.


Modern atom
Modern Atom throughout history.

  • Electrons

  • Protons

  • Neutrons


Alpha beta particles
Alpha & Beta particles throughout history.

http://wps.prenhall.com/esm_brown_chemistry_9/0,4647,169289-,00.html


Electrons
Electrons throughout history.

  •  Electrons are tiny particles which behave like clouds

  • Electrons carry something called a negative electric charge.

  • Electrons are responsible for the chemistry of the atom.


Electrons http education jlab org atomtour listofparticles html
Electrons throughout history.http://education.jlab.org/atomtour/listofparticles.html


Atoms1
Atoms throughout history.

- Atomic diameter ~ 1 to 5x10-8 cm

- Are about 10,000,000 in 1 mm

- An H atom weighs 1.67x10-24 g

  • Note: (6.02x1023) x (1.67x10-24 g) = 1.00 g

  • 6.02x1023 = Avogadro’s Number


Atoms are made up of three major parts: throughout history.

Part Found Mass Charge

Electrons Outside 9.1x10-28g (small) -1

Protons Nucleus 1.7x10-24g (1.0 AMU) +1

Neutrons Nucleus 1.7x10-24g (1.0 AMU) 0


Atomic structure
Atomic Structure throughout history.

1) Neutral atoms contain equal number of electrons and protons.


Atomic structure1
Atomic Structure throughout history.

2) Atoms can loose or gain electrons to become charged = ions


Atomic structure2
Atomic Structure throughout history.

3) Number protons determines the identity of the atom or ion.

Atomic Number


Atomic structure3
Atomic Structure throughout history.

4) Mass Number =

# Protons + # Neutrons


  • APE throughout history.MAN

    Atomic Number

    =Proton #

    =Electron #

    Mass #

    -Atomic Number

    = Neutron #


Charge throughout history.(if ion)

Mass Number

Symbol

Atomic Number


Atomic mass
Atomic Mass- throughout history.

An isotopes contribution is determined by its relative abundance.


133 throughout history.

55

EXAMPLE

How many protons, neutrons and electrons are found in an atom of

Cs

Atomic number = protons and electrons

There are 55 protons and 55 electrons

Mass number = sum of protons and neutrons

133 – 55 = 78

There are 78 neutrons


Hydrogen throughout history.

H

1

1

Symbol

Atomic Mass

Atomic Number


Hydrogen throughout history.

Protons:

Electrons:

Neutrons:

H

1

1


Hydrogen throughout history.

Protons: 1

Electrons:

Neutrons:

H

1

1


Hydrogen throughout history.

Protons: 1

Electrons:1

Neutrons:

H

1

1


Hydrogen throughout history.

Protons: 1

Electrons:1

Neutrons:0

H

1

1


Sodium throughout history.

Protons:

Neutrons:

Electrons:

Na

23

11


Sodium throughout history.

Protons: 11

Neutrons:

Electrons:

Na

23

11


Sodium throughout history.

Protons: 11

Neutrons:

Electrons: 11

Na

23

11


Sodium throughout history.

Protons: 11

Neutrons:

Electrons: 11

12

Na

23

11

12


Rhenium throughout history.

75

Protons:

Neutrons:

Electrons:

Re

111

186

75

75

111


Rhenium Isotope throughout history.

75

Protons:

Neutrons:

Electrons:

Re

112

187

75

75

112


Re-111 throughout history.


C- throughout history.12

C

12

6


Isotopes
Isotopes throughout history.

  • Atoms of a given element with differing numbers of neutrons are called isotopes.


Isotopes1
Isotopes throughout history.

  • An atom is still the same element if it is missing an electron. The same goes for isotopes. They are still the same element. They are just a little different from every other atom of the same element.


Atomic weight
Atomic Weight- throughout history.

An isotopes contribution is determined by its relative abundance.


Atomic numbers are whole numbers throughout history.

Mass numbers are whole numbers

The atomic mass is not a whole number.


Calculating atomic mass
Calculating Atomic Mass throughout history.

atomic mass =

(% abundance of isotope 1)(mass of isotope 1) +

(% abundance of isotope 2)(mass of isotope 2) +

(% abundance of isotope 3)(mass of isotope3) +...


Calculating atomic mass1
Calculating Atomic Mass throughout history.

Answer the following questions:

"How many naturally occurring isotopes does carbon have?"

"What is the abundance of each of the isotopes?"


The sum of all the fractions of abundance throughout history.

of each naturally occurring isotopes

should equal 1.00 or 100%.


atomic mass of carbon = throughout history.

(0.9893)(12.000 amu)

+(0.0107)(13.00 amu)

= 11.868 amu + 0.1391 amu

= 12.0107 amu


What is the atomic mass of lithium
What is the atomic mass of Lithium throughout history.

Isotope Atomic Relative

Mass Abundance

Li-6 6.015 7.59

Li-7 7.016 92.41


What is the atomic mass of lithium1
What is the atomic mass of Lithium throughout history.

0.0759*6.015 =

+ 0.9241* 7.016 =

0.4565

6.4828

6.9393



What is the atomic mass of oxygen1
What is the atomic mass of Oxygen throughout history.

0.99757*16 =

+ 0.00038*17=

+ 0.00205*18=

15.96112

0.00646

+0.0369

16.00448


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