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What is the Beta-Minus Decay?
Grade Level:
Class 12
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Definition
What is it?
Beta-minus decay is a type of radioactive decay where an unstable atomic nucleus transforms into a more stable nucleus by emitting a beta-minus particle (an electron) and an antineutrino. In this process, a neutron inside the nucleus changes into a proton.
Simple Example
Quick Example
Imagine a cricket team has too many bowlers and not enough batsmen. To make the team more balanced, one bowler 'transforms' into a batsman. Similarly, in beta-minus decay, a nucleus with 'too many' neutrons converts one neutron into a proton to become more stable.
Worked Example
Step-by-Step
Let's see how Carbon-14 (C-14) decays into Nitrogen-14 (N-14) via beta-minus decay.
Step 1: Identify the parent nucleus: Carbon-14. Its atomic number is 6 and mass number is 14. So, it's written as ¹⁴₆C.
---Step 2: Understand the change: In beta-minus decay, a neutron changes into a proton. This means the atomic number (number of protons) increases by 1, but the mass number (total protons + neutrons) stays the same.
---Step 3: Write the emitted particles: A beta-minus particle is an electron, written as ⁰₋₁e, and an antineutrino, written as ν̄e.
---Step 4: Apply the changes to the parent nucleus: Since the atomic number increases by 1, the new atomic number will be 6 + 1 = 7. The mass number remains 14.
---Step 5: Identify the daughter nucleus: The element with atomic number 7 is Nitrogen (N). So, the daughter nucleus is Nitrogen-14 (¹⁴₇N).
---Step 6: Write the complete nuclear equation: ¹⁴₆C → ¹⁴₇N + ⁰₋₁e + ν̄e.
Answer: Carbon-14 decays into Nitrogen-14 by emitting a beta-minus particle and an antineutrino.
Why It Matters
Understanding beta-minus decay is crucial in fields like Medicine for cancer treatment (radiotherapy) and in Space Technology for powering spacecraft (radioisotope thermoelectric generators). Scientists and engineers use this knowledge to develop new technologies and save lives, making it a powerful concept for future careers.
Common Mistakes
MISTAKE: Thinking the mass number changes during beta-minus decay. | CORRECTION: The mass number (total protons + neutrons) remains the same because a neutron simply changes into a proton, keeping the total count the same.
MISTAKE: Confusing beta-minus decay with alpha decay or beta-plus decay. | CORRECTION: Beta-minus decay specifically involves a neutron changing to a proton and emitting an electron. Alpha decay emits a helium nucleus, and beta-plus decay emits a positron.
MISTAKE: Forgetting to include the antineutrino in the decay equation. | CORRECTION: An antineutrino is always emitted along with the beta-minus particle to conserve energy and momentum, even though it has no charge and very little mass.
Practice Questions
Try It Yourself
QUESTION: What happens to the atomic number of a nucleus during beta-minus decay? | ANSWER: It increases by 1.
QUESTION: Write the nuclear equation for the beta-minus decay of Tritium (³₁H). | ANSWER: ³₁H → ³₂He + ⁰₋₁e + ν̄e
QUESTION: A radioactive isotope X with mass number 24 and atomic number 11 undergoes beta-minus decay. What are the mass number and atomic number of the daughter nucleus, and what element is it? | ANSWER: The daughter nucleus will have a mass number of 24 and an atomic number of 12. The element with atomic number 12 is Magnesium (Mg).
MCQ
Quick Quiz
Which of the following particles is emitted during beta-minus decay?
A proton
A neutron
An electron
An alpha particle
The Correct Answer Is:
C
In beta-minus decay, a neutron transforms into a proton, and an electron (beta-minus particle) is emitted from the nucleus along with an antineutrino. Protons, neutrons, and alpha particles are not emitted in beta-minus decay.
Real World Connection
In the Real World
Beta-minus decay is used in 'carbon dating' to find the age of ancient artifacts, like pottery found in archaeological sites in India. Scientists measure the amount of Carbon-14 that has decayed into Nitrogen-14 in the sample to estimate how old it is, helping us understand our history.
Key Vocabulary
Key Terms
RADIOACTIVE DECAY: The process by which an unstable atomic nucleus loses energy by emitting radiation. | BETA-MINUS PARTICLE: An electron emitted from the nucleus during beta-minus decay. | ANTINEUTRINO: A tiny, neutral particle emitted along with a beta-minus particle. | ATOMIC NUMBER: The number of protons in an atom's nucleus. | MASS NUMBER: The total number of protons and neutrons in an atom's nucleus.
What's Next
What to Learn Next
Now that you understand beta-minus decay, you can explore other types of radioactive decay like beta-plus decay and alpha decay. These concepts will help you grasp the full picture of how unstable nuclei transform and release energy.
