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Chapter 4.1
Atomic Theory
Atom

Smallest particle of an element that has
all the properties of that element

Atomic theory is the study of the nature
of atoms and how atoms combine to
form all types of matter.
Atomic Theory


Subatomic particles come together to form atoms
Particles:
1. Protons – positive particles in the nucleus
-charge is +1
-# protons = atomic #
2. Electrons – negative particles on orbits around
the nucleus
-charge is -1
-# electons = # protons= atomic #
3. Neutrons – neutral particles in the nucleus
-charge is 0
-#neutrons= mass-atomic #
Structure of the Atom
Valence
shell
Electron orbit
Proton
Neutron
Electron
Bohr-Rutherford Diagrams
Rules:
1. Calculate PEN
2. Write the number of protons and
neutrons in the nucleus with the
elemental symbol
3. Draw the number of electrons on orbits
(2 on the first, 8 on the second, 8 on
the third, unlimited on the fourth)
Draw the bohr diagram for Calcium
Draw the Bohr diagram for Oxygen
Lewis symbols
A shorthand method of drawing
representation of an element
 It shows the atomic symbol and valence
electrons are draw surrounding the
symbol
Example: Calcium

Oxygen
Homework

Complete the Bohr diagrams for the first
20 elements