Transcript I. Isotopes - Rock Hill High School

IV. Isotopes
2 or more atoms of the same element
having the same number of protons
BUT different numbers of neutrons
How does altering the neutron
number affect the properties of
an atom?
It changes its mass!
A. Because elements naturally have
different isotopes, the atomic mass
shown on the periodic table is an
average of all known isotopes.
This explains why the average is typically a
decimal.
B. Illustrating Isotopes
Hydrogen
A
Deuterium
ZX
A= atomic mass #
Z= atomic #
X= element symbol
Tritium
Commonly shown
with just atomic
mass #
Ex. Hydrogen - 2
Ex. Boron – 10
Ex. Boron - 11
1. How could you illustrate an atom of
Uranium?
2. How could you illustrate an atom of
sodium that has lost one neutron?
3. How could you illustrate an atom of
carbon that has gained two neutrons?
C. Types of Isotopes
1. Stable: the nucleus contains enough
neutrons to block the repulsive forces of
the protons. This keeps the isotope from
breaking down over time.
2. Unstable: the nucleus of the atom does
not have right amount of neutrons to
block the repulsive forces of the protons;
this makes the isotope radioactive!
D. Radioactive Isotopes
1. Radioactive isotopes have unstable
nuclei and undergo nuclear decay
(breakdown)
2. Nuclear decay involves the emission of
energy and/or particles from the nucleus
in an attempt to become more stable.
3. The energy/particles emitted from the
nucleus are termed radiation and can be
alpha or beta particles and gamma rays.
4. Isotopes disintegrate at predictable rates,
so they are useful for determining
age/measuring time. (C-14)
5. Because most elements have unstable
isotopes, there is radiation present in
almost every environment.