Alpha, beta particles and gamma rays. How does the atomic number and atomic mass number change when a radioisotope decays to produce alpha beta or gamma radiation.
Better of you gave an answer for us to comment on.
Lets sat we have the decay of
uranium (mass=235, atomic number=92)
to
thorium (mass=231, atomic number=90)
plus
He nucleus(mass=4, atomic number=2)
Note that the mass number (235=231+4) and atomic number balances (92=90+2)
So I think you can say what the changes are?
You can do the same with beta decay, but use
electron (mass=0 atomic number=-1)
When a radioisotope undergoes radioactive decay, it can emit three types of radiation: alpha particles, beta particles, or gamma rays. Let's discuss how the atomic number and atomic mass number change for each type of radiation:
1. Alpha Decay:
During alpha decay, an unstable nucleus emits an alpha particle, which consists of two protons and two neutrons -- effectively a helium-4 nucleus. As a result, the atomic number of the nucleus decreases by 2 since it loses two protons. Additionally, the atomic mass number also decreases by 4 because the alpha particle, itself, carries away two protons and two neutrons.
For example, if a radioactive nucleus with an atomic number of 92 and an atomic mass number of 238 undergoes alpha decay, the resulting nucleus will have an atomic number of 90 (92 - 2) and an atomic mass number of 234 (238 - 4).
2. Beta Decay:
In beta decay, a neutron within an unstable nucleus undergoes transformation into a proton while emitting a beta particle. A beta particle can be either an electron (identified as beta-minus or β-) or a positron (identified as beta-plus or β+). When a nucleus emits a beta-minus particle, a neutron turns into a proton, thereby increasing the atomic number by 1. However, the atomic mass number remains unchanged since the proton replaces a neutron.
On the other hand, when a nucleus emits a beta-plus particle, a proton transforms into a neutron, leading to a decrease in the atomic number by 1 (since a proton is lost) while keeping the atomic mass number constant.
3. Gamma Decay:
Unlike alpha and beta decays, gamma decay does not involve any particle emission or nuclear transformation. Instead, it involves the emission of high-energy electromagnetic radiation called gamma rays. Gamma decay occurs after alpha or beta decay as a way for the nucleus to release excess energy.
Thus, gamma decay does not alter the atomic number or atomic mass number of a nucleus since it does not involve any change in the number of protons or neutrons.
In summary, during radioactive decay:
- Alpha decay reduces both the atomic number and the atomic mass number by 2.
- Beta-minus decay increases the atomic number by 1 while maintaining the atomic mass number.
- Beta-plus decay decreases the atomic number by 1 while keeping the atomic mass number unchanged.
- Gamma decay does not cause any change in either atomic number or atomic mass number.