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Page 1: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher
Page 2: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Brief Timeline of Atomic Theory

Page 3: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Democritus

• 400BC• Greek philosopher

Page 4: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Hard Particle (Cannonball)Theory

• Proposed that they world was made up of tiny, indivisible particles moving through a void of empty space

• “atom” comes from the Greek word “atomos”, meaning indivisible (cannot be divided)

Page 5: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

John Dalton

• 1808 AD• First modern atomic theory

Page 6: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Daltons Atomic Theory

1. All matter is composed of tiny, indivisible particles called atoms

2. All atoms of an element are identical

3. Atoms of different elements are all different

4. Atoms combine in simple ratios to form compounds

Page 7: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

J.J. Thomson

• 1897-1904• “Plum Pudding Model”• Cathode Ray tube experiment

• demo

Page 9: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Cathode Ray Tube

• Thompson showed that cathode rays (electrons) were composed of negatively charged particles that separated from the gas atoms inside the tube

• Significant because: this meant that atoms are not hard, indivisible particles. Atoms are composed of smaller “subatomic” particles

Page 10: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Thomson’s Plum Pudding Model

• The atom was a hard sphere that was positively charged with negatively charged electrons that “dotted” the atom like raisins in plum pudding

Page 11: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

The discovery of radioactivity

• Henri Becquerel– 1896– Discovered that uranium ore released rays that could expose photographic film

Page 12: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

The discovery of radioactivity

• Marie & Pierre Curie– Extracted 2 new elements from uranium (U)ore: radium (Ra) and polonium (Po)

Marie Curie

Page 13: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Ernest Rutherford

Magnetic Field Experiment• Was able to separate

radioactive rays into 2 types: alpha (a) & beta (B)

• Determined that a rays were composed of helium nuclei (He +2 charge)

Gold Foil Experiment (1911)• Lead to discovery of the

nucleus, as a positively charged center of atom, containing the mass

• Most of the atom is negatively charged empty space, electrons are outside the nucleus

Page 14: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Magnetic Field Experiment

Page 15: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher
Page 17: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Gold Foil Experiment

Page 19: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Gold Foil Experiment

Page 20: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Rutherford’s Atomic Model

Page 21: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Rutherford’s “Nuclear Model”

• Most of the atom is negatively charged empty space, surrounding a small, positively charged nucleus, containing most of the mass of the atom

Page 22: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Modern Theory of Atomic Structure

• Developed by Niels Bohr, based on the science of nuclear physics

• Bohr determined that an element's position on the periodic table was related to its electron configuration.

Page 23: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Electron configuration

Electron configuration – shows how many electrons are in each energy level or “ring”

• Ex: Carbon 2-4

Page 24: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Bohr’s Planetary Atomic Model

• Niels Bohr (1922)• Determined that electronsrotate around the nucleusin discrete paths or rings

Page 25: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Planetary Model of Atomic Structure

Page 26: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Wave-Mechanical Model

• Current (modern) theory of atomic structure

• Moseley used x-ray analysis to calculate an integer for each element: these integers are the atomic numbers

Page 27: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Wave-Mechanical Model

• There is a tiny, dense positively charged nucleus at the center of a huge negatively charged electron cloud

Page 28: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Wave-Mechanical Model

Page 29: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Orbital

• Region of probability of finding an electron

Page 30: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

“The whole point:”

• The modern model of the atom is the result of many investigations that have been revised over a long period of time by many scientists

• Atomic theory song

Page 31: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Place the models of atomic structure in order from earliest to the modern theory:

Page 32: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Basic Atomic Structure

• The nucleus occupies less than 0.01% of the total volume of an atom but accounts for 99.97% of its mass. Thus most of an atom is EMPTY SPACE where the ELECTRONS are found, this is called an ELECTRON CLOUD.

• One atomic mass unit is 1/12TH THE MASS OF A CARBON-12 ATOM. This is the standard by which the masses of all other elements are determined. It is abbreviated “u”.

Page 33: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Subatomic Particles

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  Atomic Number

Mass Number NuclearCharge

# ofProtons

# of Neutrons # of electrons

2713Al            

3517Cl            

11H            

20782Pb            

Use your Periodic Table to complete the following:

Page 36: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

The only number that never changes for an element is

ATOMIC NUMBER

!!

Page 37: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Name Symbol Atomic Number

Mass Number

Charge # ofProtons

# of Neutrons

# of electrons

  199F     0      

Helium-4       0      

    11 23 0      

Nitrogen-14       0      

        0 14 14  

      32 0     16

  6429Cu     0      

    25   0   35  

        0   81 56

    53 131 0      

        0 53 74

Atomic Structure 1

Page 38: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Name-mass Symbol Atomic Number

Mass Number

Charge # ofProtons

# of Neutrons

# of electrons

 Flourine-19 199F 9  19  0 9   10  9

Helium-4  42He  2  4 0  2 2   2

 Sodium-23  2311Na 11 23 0 11   12 11 

Nitrogen-14  147N 7  14  0 7   7 7 

 Silicon-28  2814Si 14  28  0 14 14 14 

 Silicon-32  3216Si  16 32 0  16 16  16

 copper-64 6429Cu 29  64  0 29   35 29 

 Manganese-60  6025Mn 25 60  0 25  35 25 

Barium-137  13756Ba 56  137  0 56  81 56

 Iodine-131  13153I 53 131 0 53 78 53 

 Iodine-127  12753I 53  127  0 53 74 53

Atomic Structure 1

Page 39: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Phosphorus-32       0      

  146C     0      

Potassium-39       0      

      16 0     8

  5626Fe     0      

    18 40 0      

        0 29 35  

    79 197 0      

  2412Mg     0      

**Shade the columns representing the nucleons light blue

Page 40: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

ISOTOPE

• Forms of the same element having different mass due to different number of neutrons.

• Indicated by “element name-mass”

Page 41: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

158O 16

8O

Name: _______________

Mass: ________________

Protons: ______________

Neutrons: _____________

Name: _______________

Mass: ________________

Protons: ______________

Neutrons: _____________

Page 42: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Practice:Name Symbol Atomic # Mass # # Protons # Neutrons # Electrons

  235U 

         

  238U 

         

Carbon-12 

           

Carbon-13 

           

Page 43: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

The mass number on the periodic table indicates the weighted average of all the naturally occurring isotopes of an element

To calculate a weighted average:

% X mass + % X mass + …..100 100

Page 44: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Neon is naturally found in nature having 90.51% mass of 20.00u, 0.24% mass of 21.00u and 9.22% mass of 22.00u. Calculate the weighted atomic mass of neon.

Page 45: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

1.) Uranium is found naturally in nature as 3 isotopes: isotope mass % abundance U-238 238.05g 99.28 U-235 235.04g 0.7110 U-234 234.04g 0.0054

Page 46: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Calculate the weighted average atomic mass of the elements below. Show all work, round to the nearest hundredth.

a.)99.63%14N & 0.37%10N

b.)69.1%63Cu (actual mass of 63.93g) & 30.9%65Cu (actual mass of 64.93g)

c.)78.9%24Mg, 10.00%25Mg & 11.01%26Mg

Page 47: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

You can estimate which isotope is found in the highest abundance as the one with a mass closest to the mass

listed on the periodic table

Example: Chlorine-35 mass 34.969g Chlorine-37 mass 36.966g

Look on the periodic table for the mass of chlorine ____________________________

The more abundant isotope has a mass closer to the mass given on the periodic table:_____________

Page 48: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Practice: Which isotope of silicon would be found in the highest percentage?

2814Si, mass 27.977 29

14Si, mass 28.976 3014Si, mass 29.974

Why?

Page 49: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Atomic Structure 2Isotopic Notation   Number of

protonsNumber of neutrons

Number of electrons

Mass number

1.Oxygen-16 O-16 16O        2.Oxygen-18            3. Ar-40          4.     18 18    5.     16     326.   34S        7.     19 20    8.     19     419. Iron-            10.   57Fe        11.     26 32    12. Ne-20          13.     10     2214.Hydrogen-           115. H-2          16.   3H        

Page 50: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

2.) Calculate the weighted average of the following naturally occurring isotopes. SHOW ALL WORK!

a.) 95.50%7Li & 7.50% 6Li d.) 99.63%14N & 0.37%15N  

b.)80.20%11B & 19.80%10B e.) 78.9%24Mg, 10.00%25Mg, & 11.01%26Mg  

c.)95.02%32S, 0.75%33S, & 4.21%34S f.) 92.23%28Si, 4.67%29Si, & 3.10%30Si  

Page 51: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Changes in number of subatomic particles

Isotopes• Change in number of

neutrons• Same atomic number,

different mass• Same number protons,

different number neutrons

Ions• Change in number of

electrons

• A cation is positive ion, results from loss of electrons, reducing radius

• An anion is negative ion, results from gain of electrons, increasing radius

Page 52: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

IONS

• A charged part of an atom, resulting from the loss or gain of electrons

• VALENCE electrons: outermost electrons, the last number in an electron configuration

• KERNEL electrons: all electrons except valance electrons

Page 53: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Electron configuration

Electron configuration – shows how many electrons are in each energy level or “ring”

• Ex: Carbon 2-4

Page 54: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Electron configuration of sodium:

Page 55: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

2 diagrams of atomic structure:Bohr diagrams Lewis electron dot diagrams

Bohr realized that the rows on the periodic table corresponded to the number of shells of electrons

Lewis realized that the groups/families on the periodic table correspond to the number of valence electrons

This model shows the nucleus, indicating the number of protons and neutrons, surrounded by rings, representing each energy level

This model shows the element symbol surrounded by dots, representing the valence electrons. You must place one dot at each (3, 6,9,12 o’clock) location before “doubling up” (exception: Helium)

  

   

 18

9F electron configuration 2-7  

      F electron configuration 2-7  

Page 56: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

1 18

1 Bohr Atomic Structures tables to fill in the electron 4

  configurations, as shown, then  

  draw the Bohr Atomic Structure  

  for each element 1-20.  

   

1 2

1 2 13 14 15 16 17 2

7 9 11 12 14 16 19 20

               

               

               

               

3 4 5 6 7 8 9 10

2-1 2-2 2-3 2-4        

23 24 27 28 31 32 35 40

               

               

               

               

11 12 13 14 15 16 17 18

2-8-1 2-8-2 2-8-3 2-8-4        

39 40 Rules:

    1.) Show placement 2.) The nucleus is 3.) Indicate the number

    of ALL electrons represented by a center of electrons in each

    circle showing the energy level, by writing

    *use atomic # # of protons & the the number on each ring.

19 20 OR the entire # of neutrons

2-8-8-1 2-8-8-2 electron configuration ** closest to nucleus is 1st

Page 57: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

1 Directions:use your reference 181 LEWIS Electron Dot Structures tables to fill in the electron 2

configurations, as shown, then

draw the Lewis Dot Structure

for each element 1-20.

1 2 13 14 15 16 173 4 5 6 7 8 9 10

2-1 2-2 2-3 2-411 12 13 14 15 16 17 18

2-8-1 2-8-2 2-8-3 2-8-419 20 Rules:

1.) Only show 2.) Electrons are represent- ex: 3.) You must place 1 dot(e-) 4.) Exception is row 1:

outermost(VALENCE) ed as dots, placed at the at each location before for element #2, indicate

electrons 12 you double up. both electrons at the 12

*use group # 12,3,6,9 o'clock location.

or the last # in the around the

2-8-8-1 2-8-8-2 electron configuration element symbol.

Page 58: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

2 Main Types of Ions:

anion

A negative ion

Ex: Cl-, O-2

cation

A positive ion

Ex: Na+, Al+3

Page 59: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

The octet rule

Atoms will gain or lose electrons in order to have a full valence shell of 8 electrons.

Exception: Helium can have a maximum of 2 valance electrons

Page 60: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

When an atom gains 1 or more electrons

It becomes a negative ion and it’s radius increases. A negative ion is an anion.

Page 61: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

When an atom loses 1 or more electrons

It becomes a positive ion and it’s radius decreases. A positive ion is a cation.

Page 62: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

CATION ANION Definition

Results from

Indicated by What happens to radius???

Na Na+

Naming

Lewis Dot Structure

Page 63: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

  CATION ANION

 Definition

positive ion negative ion

 Results from

Loss of electron(s) Gain of electron(s)

Indicated by (+) charge (-) charge

What happens to radius???

Gets smaller Gets bigger

      

  Na Na+

 

 Naming

“Element name-ion” Change ending of element to “-ide”

Lewis Dot Structure  [Na] + ..

[:.F.:]-

 

Page 64: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

How to predict if an element will form an anion or cation:

The “electron clock”:

8/07 16 25 3

4

# valance electrons

Page 65: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Atomic Structure 3: Predicting Ions

ElementElectron

configuration

Lewis dot structure of

atomLose or gain electrons?

How many electrons lost

or gained?Ionic Charge

**

Lewis dot structure of

ion

Radius increase or decrease?

F 2-7 F gain 1 -1 F increase

Mg 2-8-2 Mg lose 2 +2 Mg decrease

O              

Al              

N              

Fr              

C              

Page 66: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

  2-8-8-1            

  2-8-7            

  2-8-18-18-8-2            

  2-8-6            

  2-8-5            

  2-3            

**In the “ionic charge” column only: shade the cation charges red and the anion charges blue

ElementElectron

configuration

Lewis dot structure of atom

Lose or gain

electrons?

How many electrons

lost or gained?

Ionic Charge

**

Lewis dot structure of

ion

Radius increase or decrease?

Page 67: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

   

 # of

Protons# of

Neutrons# of

ElectronsNuclear Charge

Bohr Diagram of Atom

Lewis Dot of Atom

PredictIonic

Charge

Lewis Dot of

IonName of Ion

ex 3517Cl 17 18 17 +17   Cl -1   Chloride

1 2311Na  

               

2 94Be  

               

3 6530Zn  

               

4 147N  

               

5 3216S  

               

6 2010Ne  

               

7 12753I  

               

8 10847Ag  

               

9 7031Ga  

               

10 126C  

               

Atomic Structure 4

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Atomic Spectra

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Radiant Energy

• Energy that travels through space as electromagnetic waves at the speed of light

Page 70: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Electromagnetic Spectrum• Includes all types of radiant energy from

gamma rays (hi E) to radiowaves (lo E)• Visible light is only a small portion of the

spectrum

Page 71: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

1 photon = 1 quantum

Quanta: tiny packets of energy released or absorbed by objects

*Einstein and Plank determined that energy is released or absorbed in a continuous flow of small packets or quantum/photons

Page 72: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Release or Absorption of Energy:

Page 73: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher
Page 74: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Higher energy levels(excited state)

Electrons absorb energy when jumping to

Electrons release energy when falling to

Lower energy levels(ground state)

Page 75: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher
Page 76: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Bohr used the emission spectrum as proof of planetary model

But his model only works for hydrogen because he didn’t account for electrons moving between energy levels

Page 77: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Spectral Lines

Characteristic wavelengths (l) of photons of energy released as electrons fall from hi to lo energy

Page 78: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Spectral lines demo:Salt of Element Color of Flame

 

Strontium Chloride 

   

Barium Chloride 

   

Copper (II) Chloride 

   

Lithium Chloride 

   

Potassium Chloride 

   

    Identity

Unknown Element 

   

Unknown Mixture 

   

Page 79: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Emission Spectrum:

Page 80: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Each element has it’s own characteristic spectrum:

Page 81: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Compare H & He:

hydrogen helium

Page 82: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Because electrons do move between energy levels, emitting “spectral lines”, we had to change our view of atomic structure:

Page 83: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Excited State Electron ConfigurationsOccurs when elements absorb energy and jump to a higher energy level.

** it will not look like it is written on periodic table, be sure they add to the correct number!

Ground state: 2-8-1Excited state : 2-7-2

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“Crib Sheet”• #p+ = atomic number *#n0 = mass-atomic

number• #e- = #p+ - charge (use the sign of the charge)• Isotope: same #p+, different #no OR same

atomic number, different mass• To calculate weighted average: (%/100 x atomic

mass) + (%/100 X atomic mass) + …..• *Ion: same # p+, different #e-

• Charge= #p+ - #e-

Page 89: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Atomic Structure Review p. 17

1. 112. 93. 434. 925. 1186. 137. 118. 4

9. Br10. C11. Sn12. Zn13. Cl14. 4015. 16

Page 90: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Atomic Structure Review p. 17

16.)

=(.925x7) + (.0750x6)

=6.475 + .45

=6.925

=6.93g

17)

=(.789x24)+(.10x25)+(.1101x26)

= 18.936 + 2.5 + 2.8626

= 24.2986

= 24.30g

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Atomic Structure Review p. 18

18.) 2-8-119.) Na20.) 2-7-221.) 1922.) 123.) Y24.) Ar25.) Not possible

27.) as electrons fall from excited state to ground state energy is released as radiant energy (spectral lines).28.) you can ID the gas element using spectral line analysis.29.) electrons are negatively charged particles. B has 5 e-, its e-config. is 2-3, with 2 e- in the 1st energy level and 3 e- in the 2nd (valence) level

Page 92: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Atomic Structure Review MC?s1.) 2 13.) 12.) 4 14.) 43.) 1 15.) 14.) 1 16.) 35.) 3 17.) 46.) 1 18.) 37.) 4 19.) 28.) 2 20.) 29.) 4 21.) 310.) 311.) 412.) 3 pg 19-20

1.) 4 13.) 22.) 3 14.) 43.) 2 15.) 34.) 3 16.) 35.) 2 17.) 26.) 3 18.) 17.) 1 19.) 18.) 2 20.) 49.) 3 21.) 410.) 1 22.) 211.) 3 23.) 312.) 1 pg 21-22

Page 93: Brief Timeline of Atomic Theory Democritus 400BC Greek philosopher

Atomic Structure Review p. 23

1.) 19p, 20n, 18e 2.) 9p,10n,10e3.) 5p,6n,2e 4.) 15p,16n,18e5.) 16p,16n,18e 6.) 14p,14n,10e7.) 7p,7n,10e 8.) 20p,20n,20e9.) 37p,48n,36e 10.) 53p,75n,54e11.) 30p,35n,28e 12.) 6p,6n,10e