Download Beyond Element 83 are very unstable (radioactive)

TOPIC: Radioactivity & Natural
Transmuations
Do Now: Where on your reference
table can you find radioactive
particles?
Not all isotopes are stable
Stable isotopes have…
1:1 ratio of n0 to p+
(for elements <20)
1.5:1 ratio of n0 to p+
(for elements >20)
Beyond Element 83 are very
unstable (radioactive)
• No amount neutrons can hold nucleus together
once it has 83+ protons
• All Elements 83 and above on PT
are radioactive
• Other elements may have radioactive isotopes
applet
Radioisotopes- unstable nucleus – they are
radioactive
the nucleus of element
emits subatomic particles
and/or electromagnetic
waves…
by emitting these particles,
nucleus changes into
different element (it’s trying
to become more stable)
Radioactive Decay Series
• Sometimes 1 transmutation isn’t enough
to achieve stability
• Some radioisotopes go through several
changes before they achieve stability
(and are no longer radioactive)
U-238  PB-206
Transmutation-When an element turns into a different
element. This occurs when the number of protons
changes.
These subatomic particles that are
emitted were discovered around 1900
• Alpha rays
• Beta rays
• Gamma rays
Radioactivity – Rutherford again!
Penetration & Shielding
2 Neutrons &
2 Protons
Charge = +2
Mass = 4amu
4 He
2
Beta Particle – fast moving electron
Transmutation
• 2 types
–Natural
–Artificial
Natural Transmutation
Happens all by itself (spontaneous)
Not affected by anything in environment
• 1 term on reactant side
• Original isotope
• 2 terms on product side
• Emitted Particle
• New Isotope
Natural Transmutation
16N
7

1 term on
reactant side
0e
-1
+
16O
8
2 terms on
product side
Balancing Nuclear Equations
16N
7

0e
-1
+
16O
8
Conservation of mass number:
16 = 0 + 16
Conservation of atomic number:
7 = -1 + 8
so Y = 228
232 = 4 + Y
232Th
90

4He
2
+
Y
X
Z
Conservation of Mass Number:
sum of mass numbers on left side must =
sum of mass numbers on right side
232Th
90
 42He + 228
X
Z
90 = 2 + Z
so Z = 88
Conservation of Atomic Number:
sum of atomic numbers on left side must =
sum of atomic numbers on right side