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Atomic Structure
ATOMIC THEORY: from 440 B.C. to present

I. 440 B.C. : Leucippus and Democritus

A. All matter is composed of atoms....These atoms cannot be further split into smaller portions.

B. There is a void, which is empty space between atoms.

C. Atoms are completely solid.

D. Atoms are homogeneous, with no internal structure.

E. Atoms are different in their sizes, their shapes, and their weight.


II. 1766 - 1844 : John Dalton ďThe Father of Atomic TheoryĒ

Four basic ideas in Daltonís atomic theory:

A. Chemical elements are made of ______________

Atoms are ____________, ___________________ particles

B. The atoms of an element are _________________ in their masses



                 Zn           =            Zn             =            Zn



C. Atoms of different elements have different masses






_____ LIGHTEST     _____ HEAVIER       _____ VERY HEAVY


D. Atoms only combine in small,  _____________________ 

Law of Definite Proportions

Observation: Every time we make zinc chloride, the ratio comes out to
_________________________

- or -

0.92 g Zn
1.00 g Cl

If all ... Zn atoms have a mass of 65 units
and all ... Cl atoms have a mass of 35 units

Then, 1 atom Zn =     _______   =    _______ 
          1 atom Cl 

But ...

We got ... 0.92 g Zn 
                1.00 g Zn

Conclusion: _____________________________________


1 atom Zn = ________ = ________ 
2 atoms Cl 


                = ZnCl =  white  substance


Daltonís Atomic Model





Two of these (Daltonís items A - D) are now known to be wrong ______ and ______ 


III. 1856 - 1940 John Joseph (J. J.) Thomson

Thomsonís Cathode-Ray Tube


Observations:

1) Something went across the tube. Was it ____________ or _____________ ?

2) Put in a pin wheel: found that it ____________

3) Easily ______________ by a ________________

4) With different ______________ or different ______________: always the same results

5) Light rays were deflected toward the _____________


Conclusions: 

1) ________________________________________________________________
__________________________________________________________________

2) These cathode ray particles are ___________________ charged.  These particles were

later named _______________________.

3)___________________________________________________________________________________________________________________________________

4) Thomson used magnetic and electric fields to measure the ratio of the electron's mass to its charge.  He estimated that the electron's 

mass was ______________ the mass of the hydrogen atom.

Thomsonís Atomic Model






IV. 1868 - 1953 Robert Millikan

Millikanís Oil Drop Experiment

Conclusion:

1) The ____________ on an electron is _____________

2) The _________ of an electron is _____________

Va.    ~ 1896 Eugene Goldstein

1) modified the cathode ray tube used by Thomson: ____________________________

___________________________________________________________________

2)  observed rays traveling in the direction opposite to that of the cathode rays:

_____________  _____________

3) concluded that they were composed of _______________ ________________

4) the positive particles had a charge opposite and equal to the negatively charged particles

of Thomson's experiments (atoms that had lost electrons and become ions)



V. 1871 - 1937 Ernest Rutherford 

To test the Thomson model of the atom, __________________ did a famous experiment:

Rutherfordís Gold Foil Experiment


Observations:

1) Most of the particles passed directly through - no deflection

2) Some of the particles were deflected somewhat from their path.

3) Some of the particles bounced back in the same direction from which they approached the gold foil.

Thomsonís Model says: all particles should go through and ...
he canít explain the 1/20,000 that deflected
back ...
So, Rutherford proposed his own atomic model:

Conclusions:

1)  ____________________________________________________________________

2)  ____________________________________________________________________
_______________________________________________________________________

3) ____________________________________________________________________
_______________________________________________________________________



Rutherfordís Atomic Model:

Atoms have a _________________, _______________, which he called the _____________________.










VI. James Chadwick

An atom contains ________ __________  around a ___________   ___________. Are there any ________ 

____________ in the atom? In 1932, _______________ did an experiment to find out.










Observation: Chadwick found that _______changed to _______ 


Conclusion: ________ ________ came out: called ________



VII. A. Parts of the Atom:




Names: 

Size: 

Mass present: 

Subatomic              
Particles 
present: 


B.  Properties of the Three Key Subatomic Particles

Name                                Charge                                             Mass

(Symbol)                Relative        Absolute (C)      Relative(amu)       Absolute (g)

                                                      + 1.6 x 10-19                                                  1.67262 x 10-24

                                                              0                                               1.67493 x 10-24

                                                      - 1.6 x 10-19                                                  9.10939 x 10-28

The number of ________________ determines what element you have.

This is called the ___________ _________________:  the symbol for atomic number is _______

If Z = 14, the atom is _______

For Cl, Z = _______

The total number of protons and neutrons is called the _________ ________ : the symbol for the mass number is _______

Carbon, C, has _____ protons and ______ neutrons; A = _______

___________________ is a shorthand way to show what is in a ___________


A
Z X

A = ________________________________________________________
Z = ________________________________________________________
N = A - Z = _________________________________________________




Nuclear Notation:

                     9 P
                    10 n       = 



                     49 P
                     66 n     =



12                  ________ protons
     C               ________ neutrons
  6


59                  ________ proton

      Co           ________ neutrons

27                       



128                  ________ protons
     Te               ________ neutrons
52 

 __________________: same__________ different _________ because of different number of ____________


Three Isotopes of Hydrogen


             1                             2                               3
             1 H                         1 H                           1 H

Name: ____________      ____________         ______________

           ______   proton       _____ proton           _____ proton 

            _____ neutrons        _____ neutrons        _____ neutrons



Two common Isotopes of Uranium:



238                                ____
___ U                             ____ U

______ protons             ______ protons

______ neutrons            143 neutrons

VIII. Atomic Mass System 

How can we find the mass of one atoms? They are much to small for us to measure - so we develop a relative scale:














Definition: _________________________________________________________

therefore, the mass of 1 H atom is _______,________

(Note: 1 ________ = 1.67 x 10-24 g)

____________    is the standard mass and the mass of all other atoms is measured relative to C

What is the atomic mass of carbon according to the periodic table?

______________________

Why?
The 12.011 amu is the_________  mass of carbon atoms in nature. The number of ________ in the 

nucleus of every carbon atom is __________, but the number __________of can vary. The ________ 

_____________ of carbon atoms (or atoms of any element) can vary. The most common form of carbon is:

_____________________________________

Use this isotope notation (element name - mass number) to name the other two naturally occurring isotope of carbon:
_______________ 

_______________

Example:  Determine number of subatomic particles in the isotope of an element

Silicon (Si) is essential to the computer industry as a major component of semiconductor chip.  It has three 

naturally occurring isotopes: Silicon-28, Silicon-29, and Silicon-30.  Determine the number of protons, neutrons, 

and electrons in each silicon isotope:

 

 

 

Example: How many protons, neutrons, and electrons are in each of the following:

(a)                                                  (b)                                          (c)        

 

What element symbols do Q, X, and Y represent?

Example: Calculating the atomic mass of an element             

Oxygen exists in nature in three forms:
                                            

Oxygen-16 
Oxygen-17
Oxygen-18 

What is the number of protons, neutrons, and electrons in each isotope?

                                        protons        neutrons        electrons
Oxygen-16 
Oxygen-17 
Oxygen-18 

Calculate the average atomic mass of oxygen atoms given the following isotopic data:

ISOTOPE                        MASS (amu)                          ABUNDANCE

                                                                                       %            Fractional

Oxygen-16                        15.99491 amu
Oxygen-17                        16.99914 amu
Oxygen-18                        17.99916 amu 

The ____________ _______________ ________________ of oxygen is:

 



Oxygen-16                            0.99759 (15.99491 amu) 
Oxygen-17                         + 0.00037 (16.99914 amu)
Oxygen-18                         + 0.00204 (17.99916 amu)




Example: In nature, copper is found to exist in two forms: copper-63 and copper-65. Copper-63 atoms 

have a mass of 62.93 amu, while copper-65 atoms have a mass of 64.93 amu. Naturally occurring copper

 contains 69.40% copper-63. Calculate the atomic mass of naturally occurring copper atoms.

 




IX. The Periodic Table - continued

A. Dmitri Mendeleev
   1836 - 1907

- Professor of Chemistry at University of St. Petersburg

- Developed the periodic table while writing a chemistry textbook for his students

- Based on the observation that when the elements were arranged in order of their

weight (mass) , similar chemical properties repeated at periodic intervals

- German physicist Julius Lothar Meyer developed similar periodic table within

the same time period as Mendeleev

B. 1887 - 1915 Henry Moseley

- English physicist

- Discovered that every element had a different number of protons

- Arranged the elements in a table by order of atomic number instead of atomic mass

C. The Modern Periodic Table

_________- the horizontal rows (identified by a number)
_________- the vertical columns (identified by a number and a letter

Any element can be located with a period number and group number 

Na is located in Period _____, Group ______ 
O is located in Period   _____, Group ______ 
Fe is located in Period  _____, Group ______

Group A elements (IA - VIIA) are the ____________________________

Group B elements are the ________________________ ______________ and 

_____________ ______________________ ________________

Family names on the Periodic Table:


- Group IA elements are the ___________________
- Group IIA elements are the ___________________
- Group VIIA elements are the ___________________

- Group VIIIA elements are the_________________ or ______________________

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