Lec: Isotopes and Ions. An Isotope is an element that has the same number of protons but a different...
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Transcript of Lec: Isotopes and Ions. An Isotope is an element that has the same number of protons but a different...
Example: C12,C13, and C14 have 6 protons but 6, 7, and 8 neutrons. The combination of the # of protons and neutrons equals the isotope #.
The nuclei of C12,C13, and C14
C12 = 6 protons 6 neutrons
C13 = 6 protons 7 neutrons C14 = 6 protons 8 neutrons
Protons= Neutrons=
C12 C1
3
C14
All protons have a +1 electrical charge.All electrons have a -1 electrical charge.If an atoms protons and electrons are the same the atom is neutral.
An ion with a negative (-) electrical charge is an anion.
Examples of anions are expressed like this:
F- or C-2
Fluorine (F) has gained an electron thus changing F to a (-1) electrical charge. Carbon (C) has gained two electrons thus changing the electrical charge to -2.
Example of an ion for F-
Fluorine according to your PTE should have 9 electrons and protons however F- has 10 electrons and 9 protons.
An ion with a positive (+) electrical charge is an cation.
Examples of cations are expressed like this:
Li+ or C+2
Lithium (Li) has lost an electron thus changing Li to a (+1) electrical charge. Carbon (C) has lost two electrons thus changing the electrical charge to +2.
Example of cation for Li+
Lithium according to your PTE should have 3 electrons and protons however Li+ has 2 electrons and 3 protons.
Gamma RayAn electromagnetic wave similar to X-rays. It can not be detected by your eyes. Gamma rays move at the speed of light.
Half-Life: The time it takes for a radioactive isotope total mass to decay by one half. A half-life can be anywhere from fractions of a second to millions of years. Example: U238 has a half-life over 4.5 billion years and Po214 is 0.0000016 second.
The half-life of Ra222 at the end of 0 half life. 100% still radioactive radon.
0102030405060708090
100
%
0 1 2 3 4
Half-Life
Polonium 214Radon 222
The half-life of Ra222 at the end of 1st half life. 50% still radioactive radon.
0102030405060708090
100
%
0 1 2 3 4
Half-Life
Polonium 214Radon 222
The half-life of Ra222 at the end of 2nd half life. 25% still radioactive radon.
0102030405060708090
100
%
0 1 2 3 4
Half-Life
Polonium 214Radon 222
The half-life of Ra222 at the end of 3rd half life. 12.5% still radioactive radon.
0102030405060708090
100
%
0 1 2 3 4
Half-Life
Polonium 214Radon 222
The half-life of Ra222 at the end of 4th half life. 6.25% is still radioactive radon.
0102030405060708090
100
%
0 1 2 3 4
Half-Life
Polonium 214Radon 222
Calculating the half-life of Ra222. Ra222 has a half-life of 4 days and starting mass of 800g.
# of half lives
Time %Radioactiv
e
Mass radioacti
ve
0
1
2
3
4
1st half life
# of half lives
Time %Radioactiv
e
Mass radioacti
ve
0 0 days 100 800 g
1 4 days 50 400 g
2
3
4
2nd half-life
# of half lives
Time %Radioactiv
e
Mass radioacti
ve
0 0 days 100 800 g
1 4 days 50 400 g
2 8 days 25 200 g
3
4
3rd half-life
# of half lives
Time %Radioactiv
e
Mass radioacti
ve
0 0 days 100 800 g
1 4 days 50 400 g
2 8 days 25 200 g
3 12 days 12.5 100 g
4
4th half-life
# of half lives
Time %Radioactiv
e
Mass radioacti
ve
0 0 days 100 800 g
1 4 days 50 400 g
2 8 days 25 200 g
3 12 days 12.5 100 g
4 16 days 6.25 50 g
Bismuth, Bi214 has a half-life of 20 minutes, how much will still be radioactive when it reaches its 4th half-life and when will this occur? The starting radioactive mass is 200g.
4th half-life# of half
livesTime %
Radioactive
Mass radioacti
ve
0 0 minutes
100 200 g
1 20 minutes
50 100 g
2 40 minutes
25 50 g
3 60 minutes
12.5 25 g
4 80 minutes
6.25 12.5 g