1. Atomic Theory

2. Atoms are the smallest unit of
matter and make up everything
in the universe.
Every atom is made up of three
different subatomic particles:
1. Protons
2. Electrons
3. Neutrons

3. The central region of the atom is called the nucleus and
consists of protons and neutrons.
Electrons orbit the nucleus
in ring-like areas called
electron orbitals.**
Protons = positive charge
Electrons = negative charge
Neutrons = neutral charge
**orbitals show where an
electron MIGHT be.

6. The periodic table is used to organize elements based on
their physical and reactive characteristics/trends.
Groups = vertical columns Periods = horizontal rows

8. Using the Periodic Table
The periodic table can be used to find information about the
various elements.
Atomic Mass
Average sum of
# of protons
+
# of neutrons
(average weight)
Atomic Number
Number of protons
an atom has.

9. Most atoms are electrically neutral, which means that the
# of protons = # of electrons
Atomic Mass
Average sum of
# of protons
+
# of neutrons
(average weight)
Atomic Number
Number of protons
an atom has.

10. Symbolic Notation
Oxygen
O
XZ
A
Atomic Mass
Rounded
Atomic Number
Element
Chlorine
Cl

12. Name Mass Charge Location
Proton (P+) 1 amu +1 Nucleus
Electron (e-) 1/2000 ≈ 0 -1 Orbital
Neutron (No) 1 amu 0 Nucleus
Parts of an atom
• 1 protons or 1 neutrons = 1 atomic mass unit (amu)
• 1 amu = 1.66 x 10-30 g
• electrons have negligible mass

13. Parts of an atom

14. The Bohr model is a model used to show how electrons are
organized in orbitals around the nucleus.
Each circle around the
nucleus represents an
orbital. Each orbital is able
to hold a certain number of
electrons.
#1 – 2 electrons
#2 – 8 electrons
#3 – 8 electrons
#4 – 2 electrongs

15. Electrons fill in orbitals from the inside outwards

16. Valence electrons are electrons that fill the outermost shell of
an atom. All atoms want to have a full outer layer and will
undergo reactions to receive or give away electrons.

17. HW = Fill out Bohr Model Sheet for first 21 elements.
Review Q’s
1. Where is the proton located?
2. What is the charge and mass of a neutron?
3. How many protons, electrons and neutrons are in the
following?
a) H
b) Cl
c) C
d) Fe-2
4. Draw the Bohr model for the Oxygen