1. Atomic Structure

2. Subatomic Particles
Empty Space

3. Subatomic
Particle
Actual Mass
Relative
Mass
Atomic Mass
Units
Proton
1.673 x 10-24
g
1 1
Neutron
1.675 x 10-24
g
1 1
Electron
9.11 x 10 -28
g
1/1840
Approximately
0
•Atomic Mass Unit (AMU) = is defined as 1/12
the mass of a carbon – 12 atom

4. Atomic & Mass Number
• Atomic number:
• Mass number:
• Atomic Number =
number of protons in nucleus
• Mass number =
protons + neutrons

5. Number of electrons
• For a neutral atom:
number of protons = number of electrons
• Atomic number:
(# of protons)
• Number of electrons:
• Mass number:
(p+
+ n0
)

6. Isotope Notation
• Atomic Number = number of protons in nucleus
• Mass number = protons + neutrons
• Number of neutrons = Mass number – atomic number
• Number of neutrons:

7. Examples
1. Neon – 20
– Protons:
– Neutrons:
– Electrons:
– Atomic #:
– Mass #:
– Isotope Notation:
2. Iron – 56
– Protons:
– Neutrons:
– Electrons:
– Atomic #:
– Mass #:
– Isotope Notation:

8. Isotopes
• Definition:
– Atoms of the SAME element, but different MASS
• What is different between these 3 atoms?

9. Atom OR Ion?
K
– Protons:
– Neutrons:
– Electrons:
– Atomic #:
– Mass #:
K+1
– Protons:
– Neutrons:
– Electrons:
– Atomic #:
– Mass #:

10. Atom OR Ion?
S
– Protons:
– Neutrons:
– Electrons:
– Atomic #:
– Mass #:
S-2
– Protons:
– Neutrons:
– Electrons:
– Atomic #:
– Mass #:

11. Band of
Stability

12. Radioactive
• Low Mass
– Elements 1-20
– Stable – n/p ratio = 1
– Unstable – Above or
Below
• Middle Mass
– Elements 21-83
– Stable – n/p ratio =
• 1 to 1.5
Unstable – Above or
Below
•NOTE: All atoms of elements above 83 are
radioactive!!!

13. Radioactive
• Radioactive
– Elements 84 and above
(all isotopes)
– n/p ratio is too large
• Conclusions:
– Number n0
= number p+
 Stable
– Atoms above or below this ratio  Unstable
– More mass  Unstable (radioactive)

14. Radioactive
• Lithium - 8
• Number protons:
• Number neutrons:
• n/p =
• Lead - 214
• Number protons:
• Number neutrons:
• n/p =

15. Radioisotopes
• Definition:
– a radioactive isotope of an element; produced
either naturally or artificially