Isotope Half Lives

Half-Lives of Commonly Used Radioisotopes

Isotope	Half-Life
3H	12.26 years
14C	5730 years
22Na	2.62 years
32P	14.28 days
35S	87.9 days
42K	12.36 hours
45Ca	163 days
59Fe	45.6 days
125I	60.2 days
203Hg	46.9 days
	memorize

 

Reference: p.385 of of Lubert Stryer's "Biochemistry" 3rd Edition, 1988, W. H. Freeman, New York (ISBN=0-7167-1843-X).

 

Isotope	Half-Life	Area of Body Studied
131I	8.1 days	Thyroid
59Fe	45.1 days	Red Blood Cells
99Mo	67 hours	Metabolism
32P	14.3 days	Eyes, Liver, Tumors
51Cr	27.8 days	Red Blood Cells
87Sr	2.8 hours	Bones
99Tc	6.0 hours	Heart, Bones, Liver, Lungs
133Xe	5.3 days	Lungs
24Na	14.8 hours	Circulatory System
		memorize

 

Reference: Ch.21 of "Chemistry" by Stephen S. Zumdahl, 1986, D. C. Heath and Company (ISBN=0-669-04529-2).

Half-Life Problems

In the following, the equation M(t)=M₀ 2^-t/t_1/2 holds.

 

Fill in the blank	Answer
____ of M0 remains at time t if the half-life is t1/2	M0 2-t/t1/2
M of ____ remains at time t if the half-life is t1/2	M 2t/t1/2
M of M0 remains at time ____ if the half-life is t1/2	t1/2 ln(M0/M)/ln(2)
M of M0 remains at time t if the half-life is ____	t ln(2)/ln(M0/M)
____ of 800g remains at 6 hours if the half-life is 2 hours	100g
____ of 400g remains at 4 hours if the half-life is 4 hours	200g
20g of ____ remains at 5 hours if the half-life is 2.5 hours	80g
10g of ____ remains at 5 hours if the half-life is 1 hour	320g
125g of 500g remains at ____ if the half-life is 2 hours	4 hours
10g of 640g remains at ____ if the half-life is 0.25 hour	1.5 hours
100g of 800g remains at 9 hours if the half-life is ____	3 hours
2g of 32g remains at 8 hours if the half-life is ____	2 hours
	memorize

General Nuclear Reactions

The information in all of the following sections comes from

Ch.21 of "Chemistry" by Stephen S. Zumdahl, 1986,
D. C. Heath and Company (ISBN=0-669-04529-2).

 

Fill in the blank	Answer
X in AZX is the ____	symbol for a particular element
Z in AZX is the ____	atomic number
Z in AZX is the ____	number of protons in a nucleus
A in AZX is the ____	mass number
A in AZX is the ____	sum of protons and neutrons in a nucleus
A-Z in AZX is the ____	number of neutrons in a nucleus
Each of 126C, 136C, and 146C is an ____ of C	isotope
0-1e is a ____	beta particle or β particle
0-1e is an ____	electron
01e is a ____	positron
42He is an ____	alpha particle or α particle
42He is a ____	helium nucleus
00γ is a ____	gamma ray or γ ray
10n is a ____	neutron
11H is a ____	proton
1-1H is an ____	anti-proton
126C	carbon-12
136C	carbon-13
146C	carbon-14
23892U	uranium-238
Unstable nuclides with A-Z >> Z have too many neutrons and decay via spontaneous ____ production	beta particle or β particle
Unstable nuclides with A-Z << Z have too many protons and decay via spontaneous ____ production	positron
	memorize

Stability of Nuclei

 

Fill in the blank	Answer
All nuclides with 84 or more protons are ____ with respect to radioactive decay	unstable
Light nuclides are ___ when Z equals A-Z, that is, when the neutron/proton ratio is 1	stable
For heavy nuclides to be ____, the neutron/proton ratio must be larger than 1, and this ratio rises with Z	stable
A nuclide with an odd number of protons tends to be more ____ than one with an even number of protons	unstable
A nuclide with an odd number of neutrons tends to be more ____ than one with an even number of neutrons	unstable
Nuclides with a magic number (2, 8, 20, 28, 50, 82, or 126) of protons or neutrons are especially ____	stable
	memorize

Miscellaneous Nuclear Reactions

For this chart and the ones that follow, in each reaction, make sure that all the superscripts on the left side of the arrow give the same total as all the superscripts on the right side. Also make sure that all the subscripts on the left side of the arrow give the same total as all the subscripts on the right side.

 

Reactions marked with (*) below are exceptions to the above rules
because they convert energy into matter via E=mc².

 

Fill in the blank	Answer
13153I -> 13154Xe + ____	0-1e
2211Na -> 2210Ne + ____	01e
0-1e + ____ -> 00γ	01e
20180Hg + ____ -> 20179Au + 00γ	0-1e
22789Ac -> 22790Th + ____	0-1e
7333As + ____ -> 7332Ge	0-1e
Excited State Nucleus -> Ground State Nucleus + ____	00γ
116C -> 115B + ____	01e
23793Np -> 23391Pa + ____	42He
19579Au + ____ -> 19578Pt	0-1e
3819K -> 3818Ar + ____	01e
147N + ____ -> 178O + 11H	42He
2713Al + ____ -> 3015P + 10n	42He
10n -> 11H + ____	0-1e
11H + 10n + lots of energy(*) -> 2 11H + 1-1H + ____	10n
4019K -> 4020Ca + ____	0-1e
0-1e + ____ -> 2 00γ	01e
21H + 31H -> 10n + ____	42He
	memorize

Carbon-Dating

 

Fill in the blank	Answer
146C -> 147N + ____	0-1e
147N + ____ -> 146C + 11H	10n
	memorize

Nuclear Fission

 

Fill in the blank	Answer
10n + 23592U -> 14256Ba + 9136Kr + 3 ____	10n
10n + 23592U -> 13752Te + 9740Zn + 2 ____	10n
	memorize

Breeder Reactors

 

Fill in the blank	Answer
23892U + ____ -> 23992U	10n
23992U -> 23993Np + ____	0-1e
23993Np -> 23994Pu + ____	0-1e
	memorize

Fusion in the Sun

 

Fill in the blank	Answer
11H + 11H -> 21H + ____	01e
11H + 21H -> ____	32He
32He + 32He -> 2 11H + ____	42He
32He + 11H -> 42He + ____	01e
	memorize

Carbon-Nitrogen Cycle in the Sun

Fill in the blank	Answer
126C + ____ -> 137N + 00γ	11H
137N -> 136C + ____	01e
11H + ____ -> 147N + 00γ	136C
11H + ____ -> 158O + 00γ	147N
158O -> 01e + ____	157N
11H + 157N -> 42He + 00γ + ____	126C
4 11H -> 2 01e + ____	42He
	memorize

Syntheses of Transuranium Elements

 

Fill in the blank	Answer
23892U + ____ -> 23992U	10n
23992U -> 23993Np + ____	0-1e
23993Np -> 23994Pu + ____	0-1e
23994Pu + 2 ____ -> 24194Pu	10n
24194Pu -> 24195Am + ____	0-1e
23994Pu + ____ -> 24296Cm + 10n	42He
24296Cm + ____ -> 24598Cf + 10n	42He
23892U + ____ -> 24698Cf + 4 10n	126C
24998Cf + ____ -> 257104Rf + 4 10n	126C
24998Cf + ____ -> 260105Ha + 4 10n	157N
24998Cf + ____ -> 263106Unh + 4 10n	188O
	memorize

²³⁸₉₂U Decay Series

 

Fill in the blank	Answer
23892U -> 23490Th + ____	42He
23892U -> 23490Th + ____ + 2 00γ	42He
23490Th -> 23491Pa + ____	0-1e
23491Pa -> 23492U + ____	0-1e
23492U -> 23090Th + ____	42He
23090Th -> 22688Ra + ____	42He
22688Ra -> 22286Rn + ____	42He
22286Rn -> 21884Po + ____	42He
21884Po -> 21482Pb + ____	42He
21482Pb -> 21483Bi + ____	0-1e
21483Bi -> 21484Po + ____	0-1e
21484Po -> 21082Pb + ____	42He
21082Pb -> 21083Bi + ____	0-1e
21083Bi -> 21084Po + ____	42He
21084Po -> 20682Pb + ____	42He
	memorize

 

Reference: Ch.21 of "Chemistry" by Stephen S. Zumdahl, 1986, D. C. Heath and Company (ISBN=0-669-04529-2).