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What is the Electron Capture?
Grade Level:
Class 12
AI/ML, Physics, Biotechnology, FinTech, EVs, Space Technology, Climate Science, Blockchain, Medicine, Engineering, Law, Economics
Definition
What is it?
Electron capture is a type of radioactive decay where an unstable atomic nucleus captures one of its own inner orbital electrons. This electron combines with a proton in the nucleus, changing the proton into a neutron and releasing a neutrino. The atomic number decreases by one, but the mass number remains the same.
Simple Example
Quick Example
Imagine a cricket team where a batsman (proton) suddenly decides to switch roles with a fielder (electron) from his own team. The batsman becomes a fielder (neutron), and the team's total number of players on the field stays the same, but the count of batsmen goes down by one. This is similar to how a nucleus changes during electron capture.
Worked Example
Step-by-Step
Let's see what happens when an unstable nucleus like Potassium-40 (K-40) undergoes electron capture:
Step 1: Start with the parent nucleus. Potassium (K) has an atomic number of 19 (meaning 19 protons) and a mass number of 40.
---Step 2: An inner orbital electron (e-) is captured by the nucleus. This electron combines with one of the protons.
---Step 3: The proton (p+) changes into a neutron (n0). A neutrino (ν) is also emitted.
---Step 4: The number of protons in the nucleus decreases by 1 (19 - 1 = 18). The number of neutrons increases by 1.
---Step 5: The atomic number changes from 19 to 18. An element with atomic number 18 is Argon (Ar).
---Step 6: The mass number (total protons + neutrons) remains 40 because a proton changed into a neutron, keeping the total count the same.
---Answer: Potassium-40 (K-40) transforms into Argon-40 (Ar-40) through electron capture. The nuclear reaction is: 40/19 K + 0/-1 e -> 40/18 Ar + ν.
Why It Matters
Understanding electron capture is crucial in fields like medicine for creating radioisotopes used in diagnostics and cancer therapy, similar to how doctors use special machines for check-ups. It's also vital in space technology for studying cosmic rays and the composition of stars, helping scientists understand the universe better, just like ISRO scientists explore space.
Common Mistakes
MISTAKE: Confusing electron capture with beta decay. | CORRECTION: In electron capture, an electron is *absorbed* by the nucleus. In beta decay (beta-minus), an electron is *emitted* from the nucleus.
MISTAKE: Thinking the mass number changes. | CORRECTION: In electron capture, a proton turns into a neutron, so the total number of nucleons (protons + neutrons) remains the same, meaning the mass number stays constant.
MISTAKE: Believing the atomic number increases. | CORRECTION: A proton is converted into a neutron, so the number of protons decreases by one, leading to a decrease in the atomic number.
Practice Questions
Try It Yourself
QUESTION: When an atom undergoes electron capture, what happens to its atomic number? | ANSWER: It decreases by one.
QUESTION: If an element with atomic number 27 undergoes electron capture, what will be the atomic number of the new element formed? | ANSWER: 26 (27 - 1 = 26)
QUESTION: Cobalt-57 (27 protons, 30 neutrons) undergoes electron capture. What is the new element formed, and what are its approximate number of protons and neutrons? | ANSWER: The new element is Iron-57 (Fe-57). It will have 26 protons and 31 neutrons (27-1=26 protons, 30+1=31 neutrons).
MCQ
Quick Quiz
Which of the following is true about electron capture?
The atomic number increases.
An electron is emitted from the nucleus.
A proton is converted into a neutron.
The mass number decreases.
The Correct Answer Is:
C
In electron capture, an inner orbital electron is captured by the nucleus, combining with a proton to form a neutron. This decreases the atomic number but keeps the mass number constant.
Real World Connection
In the Real World
Electron capture is used in medical imaging, specifically in Positron Emission Tomography (PET) scans. For example, Gallium-67, which decays by electron capture, is used to locate infections and tumors in the body. Just like how doctors use X-rays, PET scans give a detailed picture of what's happening inside, helping to diagnose diseases early.
Key Vocabulary
Key Terms
RADIOACTIVE DECAY: The process by which an unstable atomic nucleus loses energy by emitting radiation. | NUCLEUS: The central part of an atom, containing protons and neutrons. | PROTON: A positively charged particle found in the nucleus. | NEUTRON: A neutral particle found in the nucleus. | ATOMIC NUMBER: The number of protons in an atom's nucleus.
What's Next
What to Learn Next
Next, you should explore 'Beta Decay' and 'Alpha Decay'. These are other important types of radioactive decay, and understanding them will give you a complete picture of how unstable atoms transform, building on what you learned about electron capture.
