1. Topic 2 – Atomic Structure
The Atom

2. The Atom
The atom is the smallest particle of matter.

3. Element Notation
Atomic Number (AN) – Number of Protons = Number of Electrons
Mass Number (MN) – Protons + Neutrons
n = MN - AN
Example: P= N= E=

4. Composition Consists of Protons, Neutrons and Electrons. Mass (amu)
Charge
Where?
Protons 1 +1
nucleus
Neutrons
Electrons
5x10-4 -1
Energy shells

5. Notation Mass Number Atomic Number
Charge
Mass Number
Atomic Number
Mass Number: Number of Protons and Neutrons in the Nucleus
Atomic Number: Number of Protons and the number of Electrons
Charge: The losing or gaining of electrons results in a charge
± n

6. Isotopes
Different atoms of the same element containing the same number of protons but a different number of neutrons. Thus they have different mass numbers but have identical chemical properties. Physical properties differ.

7. Exercise: 6 6 6 #P _______ _______ _______ #N _______ _______ _______
Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.
12C C 14C
#P _______ _______ _______
#N _______ _______ _______
#E _______ _______ _______
LecturePLUS Timberlake

8. Radioactive Isotopes
Many isotopes are radioactive once their nucleus breaks down spontaneously.
60Co => 60 Ni + β
There are three forms of radiation:
Alpha - α
Beta - β or 0 e
Gamma - γ

9. Relative Atomic Mass
The mass of an atom when compared to the mass of 1/12 Carbon.
Find the Relative Atomic Mass of Oxygen: