Q.66 Chemistry ⭐ 360° Option Elimination Active
NEET 2021 Chemistry Question 66 Solution
Topic: Hydrogen · Official NTA Booklet Code M1
Question
Tritium, a radioactive isotope of hydrogen, emits which of the following particles?
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Verified Against NTA Final Answer Key
Option (1) : Beta (β-)
📚 Hydrogen Easy
📋 Given Parameters & Problem Setup
Radioactive Isotope Tritium (3_1 H or T)
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⏱️ Save ~15 seconds The 30-Second Exam Hall Shortcut: ⚡ NCERT Hydrogen Fact: Tritium Emits Low-Energy β⁻ Particles
Verbatim NCERT Hydrogen: "Of these isotopes, only tritium is radioactive and emits low energy particles ( years)." The nuclear transmutation is . Match Option (1)!
1 Recall hydrogen's three isotopes: Protium (), Deuterium (), and Tritium ().
2 Only Tritium is radioactive, with high neutron-to-proton ratio ().
3 To achieve nuclear stability, a neutron converts to a proton, emitting a negative beta particle () and an antineutrino.
4 Reaction: ().
5 Match Option (1).
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Why You Can 100% Trust This Shortcut: Canonical NCERT Hydrogen chapter section on Isotopes of Hydrogen.
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Step-by-Step Rigorous Workflow & Mathematical Proof
Step 1
Identifying the Isotopes of Hydrogen
Hydrogen has three naturally occurring isotopes: Protium (), Deuterium ( or ), and Tritium ( or ). Protium and deuterium are non-radioactive stable isotopes, whereas tritium is unstable.
Step 2
Radioactivity and Mode of Decay of Tritium
Tritium contains 1 proton and 2 neutrons in its nucleus. The high neutron-to-proton ratio () places it above the nuclear stability belt. Stability is achieved by beta-minus () decay, in which a nuclear neutron transforms into a proton, an electron (beta particle), and an electron antineutrino:
Step 3
Properties of Emitted Radiation
The emitted particle has very low maximum kinetic energy (), and tritium has a half-life of .
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4-Option Deep Scan
360° Option Elimination Engine Key Feature
Diagnose every choice: Know exactly why the right option works and why distractors fail.
1 1
✓ 100% Correct Verdict & Scientific Reason:
Verbatim NCERT fact: tritium decays via low-energy emission.
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Why this is airtight: None; textbook nuclear chemistry recall.
2 2
✗ Incorrect Verdict & Scientific Reason:
Alpha emission requires loss of a nucleus, impossible for a nucleus of mass 3.
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Student Fallacy (Why candidates pick this trap): Confusing heavy element decay (U, Ra) with light isotope decay.
3 3
✗ Incorrect Verdict & Scientific Reason:
Tritium decay is a pure ground-state beta decay without accompanying gamma de-excitation.
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Student Fallacy (Why candidates pick this trap): Assuming all radioactive decays release gamma rays.
4 4
✗ Incorrect Verdict & Scientific Reason:
Neutron emission does not occur spontaneously in tritium.
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Student Fallacy (Why candidates pick this trap): Assuming excess neutrons are expelled directly.
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NTA Trap Alert: Alpha vs. Beta Particle Trap
Students who associate radioactivity strictly with alpha particles often guess (Option 2). A tritium nucleus has mass number 3, making it physically impossible to emit an alpha particle (mass 4).
🛡️ How to avoid the -1 mark: Tritium has . It emits a single particle to convert into .
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Core NEET Syllabus Standard
NCERT Chemistry · Hydrogen Standard Benchmark
Core Scientific Principle Tested:
"Tritium is a radioactive isotope of hydrogen with a half-life of 12.33 years that decays by emitting low energy beta particles."
Syllabus Focus: Isotopes of Hydrogen
✓ Core NEET UG Syllabus Anchor Syllabus & Academic Standards ↗
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