half life
Time it takes for half of an isotope to decay
isotopes
Atoms of the same element having different masses because they contain different numbers of neutrons.
20
Initially, there are how many parent atoms? (Write answer as a number)
radioactive decay
A spontaneous process in which unstable nuclei lose energy by emitting radiation
parent element
The original element before it turns into another element through decay.
daughter element
the new element that results from the radioactive decay of the parent element
protons
Positively charged particles
neutron
A small particle in the nucleus of the atom, with no electrical charge
electron
A subatomic particle that has a negative charge
element
A pure substance made of only one kind of atom
15
The halflife of Na-25 is how many hours?
47 days
How long is the half-life of mercury-203?
75
Approximately what percentage of daughter material is there in ninety-four days?
88
Approximately what percentage of daughter material is present when the third half life is reached.
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?
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?
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?
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?
25 grams
Chromium-48 decays. After 25 half-lives, what part of 800 grams would remain?
gamma rays
_____ is produced during radioactive decay in the form of energy from the nucleus.
gamma rays
Which are more dangerous: gamma rays, alpha particles or beta particles?
stable
Radioactive decay stops when the nucleus becomes ___.
alpha particles and beta particles
______ and _____ are given off when a nucleus has too many protons or an unstable ratio of protons to neutrons