Name: __________________________________________________
Greeks experimented with idea of atom nearly 2,500 years ago
Matter was made up of atoms  _____________ or __________________ particles
Seashell experiment
Dalton’s Model of the Atom
1766-1844; Returned to theory of atoms
4 major postulates
1)
2)
3)
4)
Developed __________________________ (cathode ray tube) in 1870’s
First evidence for existence of ____________________
Discovered _________________ in 1897
Discovered positively charged particles surrounded by electrons
Found the ratio of the charge of an electron to its mass
Cathode ray tube experiments – advancement of ____________________ o Led to development of “plum pudding model” of the atom
Plum Pudding Model of the Atom

_______________________ experiment
Determined the _______________ and ________________ of an electron
Discovered the ________________ (dense core of atom) in 1911
Famous ________________________ experiment
Rutherford’s Model of the Atom
Discovered the _________________ o No charge, but same mass as __________________
Neutrons help disperse the strong repulsion of ______________________________ in the nucleus
Nucleus is very small compared to its mass!!
Improved on Rutherford’s work
“_______________________________” of the atom o Positive center is surrounded by electrons in defined _____________ circling the center
Bohr’s Planetary Model of the Atom
2

Bohr Model Vocabulary energy level – ground state – excited state –
Developed by _______________________________________; mathematical model
Electrons locations are based on ___________________________
Electrons are not ________________________, but ______________!
Defined “orbital”
Orbital =
Schrödinger Model of the Atom
(Quantum Mechanical Model)

Atom –

Subatomic particles –
3


Ion –
If the atom has a (+) charge, it has more ______________________________________.
If the atom has a (-) charge, it has more ______________________________________.
 Atomic symbol –

Atomic number –
 Mass number –
Calculations involving Subatomic Particles:
1.
2.
3.
4.
4

Isotopic Notation: Mass #
Atomic #
Examples:
Z
A
1)
80
35
Br
2)
40
20
Ca 2+
# of protons = # of protons =
# of neutrons =
# of electrons =
# of neutrons =
# of electrons =
3) Write the symbol for the isotope of carbon with a mass number of 13.
4) Write the symbol when A = 92 and the number of neutrons = 146.

Isotope –

Atomic mass –

Isotopic abundance (percent abundance) –
***Usually can round atomic mass on the periodic table to the nearest whole number to determine the most abundant isotope but NOT ALWAYS!!
5

Average Atomic Mass Calculations
1) Multiply the mass number of the isotope by the decimal value of the percent for that isotope
2) Add the relative masses of all of the isotopes to get the atomic mass of the element
Examples:
1.
Determine the average atomic mass of magnesium which has three isotpes with the following masses: 23.98 amu (78.6%), 24.98 amu (10.1%), and 25.98 amu (11.3%).
2.
If 90% of the Beryllium in the world has a mass number of 9 and only 10% has a mass number of 10, what is the atomic mass of Beryllium?

Radioactivity-

Radiation-

Nuclear reactions-
Types of Particles Emitted as Radioactive Isotopes Decay:
1.
2.
3.
6

Date
100 BC
1770
1800
1803
1880
1885
1900
1909
1913
1920-present
Scientist
Democritus/Greeks
Antoine Lavosier
Joseph Proust
John Dalton
William Crookes
Goldstein
J.J. Thomson
Ernest Rutherford
Niels Bohr
Schroedinger/Planck/
DeBroglie/Einstein/etc.
Discovery________________
Concept of the atom
Law of conservation of mass
Law of definite proportions
Law of multiple proportions
Atomic Model I
Cathode Rays (electrons)
Canal Rays (protons)
Plum Pudding Model
Discovers Electron
Atomic Model II
Nucleus of atom
Atomic Model III
Planetary Model of Atom
Atomic Model IV
Modern or Wave Model
Atomic Model V
7