Radioactive decay on the N–Z chart
"Radioactive decay on the N–Z chart" is a free, interactive Class 12 Physics simulation for NEET and JEE, built on the NCERT section "Radioactivity" in Nuclei. Nuclides on an N–Z chart with the stability band; each α, β⁻ or β⁺ step moves the nucleus and writes the balanced equation. NEET has asked about this idea 5 times in 10 years of papers. JEE Main asked 38 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson Radioactivity in Nuclei. Change the values and watch what happens.
What it shows
NCERT §13.6
Nuclides on an N–Z chart with the stability band; each α, β⁻ or β⁺ step moves the nucleus and writes the balanced equation.
Controls
5 to try
- Buttonα decay
- Buttonβ⁻ decay
- Buttonβ⁺ decay
- Buttonundo
- Segmentedstart ²³⁸U / ²³²Th / ²²Na / ¹⁴C
Try this
Take ²³⁸U to ²²⁶Ra in the fewest steps (three α and two β⁻)
Common mistake
Thinking α emission changes Z by 4, or that β decay changes A.
In NEET
10 years of papers
Asked 5 times in 10 years of NEET.
See the past questions: Radioactive Decay, Nuclear Binding Energy, Nuclei (chapter)
In JEE Main
42 shifts analysed
38 questions from Nuclei across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT §13.6
- Becquerel discovered radioactivity by accident in 1896. He lit pieces of uranium-potassium sulphate with visible light, wrapped them in black paper and put a piece of silver between the package and a photographic plate.
- After several hours the developed plate was blackened: the compound had given off something that passed through the black paper and the silver.
- Later experiments showed radioactivity to be a nuclear process: an unstable nucleus decays. This is radioactive decay.
- Three kinds occur in nature: α-decay, in which a helium nucleus ⁴₂He is emitted; β-decay, in which electrons or positrons are emitted; and γ-decay, in which high-energy photons (hundreds of keV or more) are emitted.
- A positron has the same mass as an electron and an exactly opposite charge; the two are a particle–antiparticle pair. When an electron and a positron meet they annihilate, giving gamma-ray photons.
- Radioactivity signals an unstable nucleus. Stable light nuclei have neutrons and protons roughly 1 : 1; for heavy nuclei the ratio rises to about 3 : 2, as extra neutrons offset the repulsion between protons. Nuclei far from these ratios are unstable.
- Only about 10% of known isotopes are stable. The rest have been made in laboratories, by bombarding stable nuclei with α, p, d, n or other particles, or identified in astronomical observations.
Questions
5 answers
- What does the "Radioactive decay on the N–Z chart" simulation show?
- Nuclides on an N–Z chart with the stability band; each α, β⁻ or β⁺ step moves the nucleus and writes the balanced equation.
- What mistake does the "Radioactive decay on the N–Z chart" simulation fix?
- A common mistake it clears up: thinking α emission changes Z by 4, or that β decay changes A.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 5 times in 10 years of papers.
- Does JEE Main ask questions from Nuclei?
- Yes. JEE Main asked 38 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "Radioactivity" in Nuclei (Class 12 Physics).
Embed this simulation
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