SMSH-PROJECTS-HALF LIFE II-10/12/23
element
A pure substance made of only one kind of atom
neutron
A small particle in the nucleus of the atom, with no electrical charge
radioactive decay
A spontaneous process in which unstable nuclei lose energy by emitting radiation
electron
A subatomic particle that has a negative charge
15 mg
Ac-228 has a half life of 6.13 hours. Approximately how much of a 240.0 mg sample would remain after one day? (Hint: round 6.13 to the nearest whole number)
5700
Approximately what is the half-life of carbon 14?
88
Approximately what percentage of daughter material is present when the third half life is reached.
75
Approximately what percentage of daughter material is there in ninety-four days?
isotopes
Atoms of the same element having different masses because they contain different numbers of neutrons.
25 grams
Chromium-48 decays. After 25 half-lives, what part of 800 grams would remain?
47 days
How long is the half-life of mercury-203?
30 minutes
If 20.0 g of a radioactive isotope are present at 1:00 PM and 5.0 g remain at 2:00 PM, what is the half life of the isotope?
20
Initially, there are how many parent atoms? (Write answer as a number)
What is the equation for the half-life?
Mf=Mi*1/2^(t/h)
protons
Positively charged particles
stable
Radioactive decay stops when the nucleus becomes ___.
50%
The half life of Uranium-238 is 4.5 billion years and the age of earth is 4.5 X 109 years. What fraction of Uranium-238 that was present when Earth was formed still remains?
75 mg
The half life of iodine-125 is 60 days. If the initially sample is 4800 mg, how much will of iodine-125 would be left after 360 days?
3200
The half life of radium 226 is 1602 years. If you have 500 grams of radium today how many grams would have been present 9612 years ago?
15
The halflife of Na-25 is how many hours?
parent element
The original element before it turns into another element through decay.
half life
Time it takes for half of an isotope to decay
gamma rays
Which are more dangerous: gamma rays, alpha particles or beta particles?
gamma rays
_____ is produced during radioactive decay in the form of energy from the nucleus.
alpha particles and beta particles
______ and _____ are given off when a nucleus has too many protons or an unstable ratio of protons to neutrons
daughter element
the new element that results from the radioactive decay of the parent element
Pd-100 has a half-life of 3.6 days. If one had 6.02 x 1023 atoms at the start, how many atoms would be present after 20.0 days?
1.28 x 1022 atoms
U-238 has a half-life of 4.46 x 109 years. How much U-238 should be present in a sample 2.5 x 109 years old, if 2.00 grams was present initially?
1.36 g
The half-life of Zn-71 is 2.4 minutes. If one had 100.0 g at the beginning, how many grams would be left after 7.2 minutes has elapsed?
12.5 g
100.0 grams of an isotope with a half-life of 36.0 hours is present at time zero. How much time will have elapsed when 5.00 grams remains?
155.6 hours
How much time will be required for a sample of H-3 to lose 75% of its radioactivity? The half-life of tritium is 12.26 years.
24.52 years
Fermium-253 has a half-life of 0.334 seconds. A radioactive sample is considered to be completely decayed after 10 half-lives. How much time will elapse for this sample to be considered gone?
3.34 seconds
After 24.0 days, 2.00 milligrams of an original 128.0 milligram sample remain. What is the half-life of the sample?
4.00 days
At time zero, there are 10.0 grams of W-187. If the half-life is 23.9 hours, how much will be present at the end of one day?
4.98 g
How long will it take for a 40.0 gram sample of I-131 (half-life = 8.040 days) to decay to 1/100 its original mass?
53.4 days
Os-182 has a half-life of 21.5 hours. How many grams of a 10.0 gram sample would have decayed after exactly three half-lives?
8.75 g
