1. History of the Atom - Timeline
Antoine Lavoisier
makes a substantial number of contributions to the field of Chemistry
J.J. Thomson discovers the electron and proposes the Plum Pudding Model in 1897
Niels Bohr proposes the Bohr Model in 1913
James Chadwick discovered the neutron in in 1932
1766 – 1844
1871 – 1937
1887 – 1961
460 – 370 BC
1700s
1800s
1900s
Erwin Schrodinger describes the electron cloud in 1926
Democritus proposes
the 1st atomic theory
John Dalton proposes his atomic theory in 1803
Ernest Rutherford performs the Gold Foil Experiment in 1909
1891 – 1974
1743 – 1794
1885 – 1962
1856 – 1940
Click on picture for more information

2. Democritus (460 BC – 370 BC)
Proposed an Atomic Theory (along with his mentor Leucippus) which states that all atoms are small, hard, indivisible and indestructible particles made of a single material formed into different shapes and sizes.
Aristotle did not support his atomic theory
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3. Image taken from: www.ldeo.columbia.edu/.../v1001/geotime2.html
Antoine Lavoisier (1743 – 1794)
Known as the “Father of Modern Chemistry”
Was the first person to generate a list of thirty-three elements in his textbook
Devised the metric system
Was married to a 13-year old Marie-Anne Pierette Paulze; she assisted him with much of his work
Was a tax-collector that was consequently guillotined during the French Revolution
Discovered/proposed that combustion occurs when oxygen combines with other elements
Discovered/proposed the Law of Conservation of Mass (or Matter) which states, in a chemical reaction, matter is neither created nor destroyed
Image taken from:

4. Image taken from: chemistry.about.com/.../John-Dalton.htm
In 1803, proposed an Atomic Theory which states:
All substances are made of atoms; atoms are small particles that cannot be created, divided, or destroyed.
Atoms of the same element are exactly alike, and atoms of different elements are different
Atoms join with other atoms to make new substances
Calculated the atomic weights of many various elements
Was a teacher at a very young age
Was color blind
Image taken from: chemistry.about.com/.../John-Dalton.htm

5. Image taken from: www.wired.com/.../news/2008/04/dayintech_0430
J.J. Thomson (1856 – 1940)
Proved that an atom can be divided into smaller parts
While experimenting with cathode- ray tubes, discovered corpuscles, which were later called electrons
Stated that the atom is neutral
In 1897, proposed the Plum Pudding Model which states that atoms mostly consist of positively charged material with negatively charged particles (electrons) located throughout the positive material
Won a Nobel Prize
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6. Ernest Rutherford (1871 – 1937)
In 1909, performed the Gold Foil Experiment and suggested the following characteristics of the atom:
It consists of a small core, or nucleus, that contains most of the mass of the atom
This nucleus is made up of particles called protons, which have a positive charge
The protons are surrounded by negatively charged electrons, but most of the atom is actually empty space
Did extensive work on radioactivity (alpha & beta particles, gamma rays/waves) and was referred to as the “Father of Nuclear Physics”
Won a Nobel Prize
Was a student of J.J. Thomson
Was on the New Zealand $100 bill
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7. Image taken from: commons.wikimedia.org/wiki/File:Niels_Bohr.jpg
In 1913, proposed the Bohr Model, which suggests that electrons travel around the nucleus of an atom in orbits or energy levels. Additionally, the electrons can jump from a path in one level to a path in another level (depending on their energy)
Won a Nobel Prize
Worked with Ernest Rutherford
Image taken from: commons.wikimedia.org/wiki/File:Niels_Bohr.jpg

8. Image taken from: nobelprize.org/.../1933/schrodinger-bio.html
Erwin Schrodinger ( )
In 1926, he further explained the nature of electrons in an atom by stating that the exact location of an electron cannot be stated; therefore, it is more accurate to view the electrons in regions called electron clouds; electron clouds are places where the electrons are likely to be found
Did extensive work on the Wave formula  Schrodinger equation
Won a Nobel Prize
Image taken from: nobelprize.org/.../1933/schrodinger-bio.html

9. Image taken from: www.wired.com/.../news/2009/02/dayintech_0227
James Chadwick (1891 – 1974)
Realized that the atomic mass of most elements was double the number of protons  discovery of the neutron in 1932
Worked on the Manhattan Project
Worked with Ernest Rutherford
Won a Nobel Prize
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10. Democritus & John Dalton
Progression of the Atomic Model + -
The structure of an atom, according to:
Democritus & John Dalton
James Chadwick
J.J. Thomson
Neils Bohr
Ernest Rutherford
Erwin Schrodinger

11. Quantum Mechanical Model
In addition to knowing that there were energy levels in the atom, three scientists began to notice other things...
Heisenberg – impossible to know the exact position and exact speed of an electron at the same time
De Broglie – electrons have wave-like properties, as in they move in wave patterns
Schroedinger – developed probability of finding each electron in a given location

12. Using the Quantum Mechanical Model
Quantum mechanics is a mathematical way of describing where electrons are located.
It is based on the probability of finding an electron in the space outside the nucleus.

13. Rules for Energy Levels
Level 1 (closest to the nucleus) can hold a maximum of 2e.
Level 2 can hold a max of 8e.
Level 3 can hold a max of 18e.
Level 4 can hold a max of 32e.
You must fill one level before going on to draw the next level!

14. NOTES: Isotopes and Ions
Warm-up ():

15. Isotopes:
Isotopes - is a version of an atom with the same number of PROTONS, but different number of NEUTRONS.
-If an atom is an isotope you name it using the element name followed by the mass number.
* Ex: carbon – 12 and carbon -14
- Writing Isotope Symbols:
Write the atomic symbol for the element
To the top left of the symbol write the mass # of the isotope.
Beneath that (to the bottom left of the symbol). Write the atomic number of the element.

16. Ex: Label the following
Carbon-14 is written like this: C
Mass # 14
Element Symbol 6
Atomic #

17. C and C 14 12 6 6 Isotope Examples:
How many protons does Carbon-14 contain?
How many protons does Carbon-12 contain? 6
How many neutrons does Carbon-14 contain?
How many neutrons does Carbon-12 contain?
14-6 = 8
12-6= 6

18. Ions are charged atoms (+ or -)
* Atoms as a rule are all neutral in charge, meaning that the number of protons and electrons in the atoms are equal.
Ions:
Ions are charged atoms (+ or -)
Formed when an atom GAINS or LOSES electrons

19. Ions Examples Lithium - 7 + Protons: 3 Neutrons: 4 Charge: 1+
Cations
Positively (+) charged atoms
Form by LOSING electrons
Usually formed by metals
Examples Lithium - 7 +
Protons: 3
Neutrons: 4
Charge: 1+
Electrons: 2

20. 2- Ions Protons: 16 Neutrons: 16 Charge: 2- Electrons: 18 Anions
Negatively (-) charged atoms
Form by GAINING electrons
Usually formed by nonmetals
Examples Sulfur - 32 2-
Protons: 16
Neutrons: 16
Charge: 2-
Electrons: 18

21. Homework Complete the table as directed on
Complete the chart and answer the questions on Pg. 8 in group of 2 (no larger!).
Homework:

22. 2+ Neutral Atom# Isotope Symbol Atom name with mass # #Protons
#Neutrons
#Electrons
Atomic Number
Mass Number
Neutral/Isotope/Ion
Charge 1
Neutral 2 3 4 5 6
 2+ 7 8 9 10 11 12

23. Isotopes and Average Atomic Mass
Isotopes and Average Atomic Mass * Compare & contrast Mass Number and Atomic Mass:

24. Atomic Mass Calculations
Atomic mass is the weighted average of the masses of all naturally occurring isotopes.
Formula Atomic Mass=
Σ[(Percent Abundance) x (Mass of Isotope)]
Σ = take the sum of; add them all up at the end!
Sample Calculations together.. 

25. Atomic Mass Calculations
Formula Atomic Mass=
Σ[(Percent Abundance) x (Mass of Isotope)]
Σ = take the sum of; add them all up at the end!
(.7553 x ) + ( x )=
35.46 amu

26. Formula Atomic Mass=
Σ[(Percent Abundance) x (Mass of Isotope)]
Σ = take the sum of; add them all up at the end!
(.7553 x ) + ( x )=
35.46 amu
Cl chlorine

27. Atomic Structure- Inside the Nucleus
Protons
Positively (+) charged particles
Equal to the atomic number
Identity of atoms is based on # of protons in Nucleus
Contribute to the mass of the atom
Proton mass = 1amu
amu= atomic mass unit

28. Atomic Structure- Outside the Nucleus (Electron Cloud)
Electrons
Negatively (-) charged particles
Responsible for the CHEMICAL PROPERTIES of the atom
In a neutral atom (no charge), protons=electrons
Very little mass
~0 amu

29. Name____________________________________________Quiz Complete the following table:
Complete Symbol
Mass Number
Atomic Number
Protons
Neutrons
Electrons 14 16 15 Se 8 10 70 34

30. 14 16 15 8 10 Se 70 34 My favorite No Complete Symbol Mass Number
Atomic Number
Protons
Neutrons
Electrons 14 16 15 Se 8 10 70 34

31. -15 Si 14 +14 16 28.09 My Favorite “No” Complete Symbol Mass Number
Atomic Number
Protons
Neutrons
Electrons Si
28.09 14
+14 16
-15

32. -15 Si 14 +14 16 70 34 O 8 10 Se 14+16 = 30 70-34 = 36 Atom quiz 1- 30
Complete Symbol
Mass Number
Atomic Number
Protons +
Neutrons
Electrons
- 1 Si
14+16 = 30 14
+14 16
-15 Se 70 34
70-34 = 36 O 8 10 1- 30 14 70 34 2- 16 8

33. +=
= Cations