Which of the following equation is not correct for β-decay?

The correct answer is Option (2) → \( p\rightarrow n+e^{-}+\nu \)

In every decay equation electric charge and mass number must balance, and the electron-type particle emitted must be accompanied by the right kind of neutrino. In \( \beta^{-} \) decay a neutron changes into a proton with the emission of an electron and an antineutrino; in \( \beta^{+} \) decay a proton changes into a neutron with the emission of a positron and a neutrino.

Option (1) \( n\rightarrow p+e^{-}+\overline{\nu} \) — Correct for \( \beta^{-} \) decay. Charge: \( 0 = +1-1+0 \).

Option (2) \( p\rightarrow n+e^{-}+\nu \) — Not correct. The charge on the left is \( +1 \) and on the right it is \( 0-1+0 = -1 \), so charge is not conserved. A proton can change into a neutron only by emitting a positron.

Option (3) \( p\rightarrow n+e^{+}+\nu \) — Correct for \( \beta^{+} \) decay. Charge: \( +1 = 0+1+0 \).

Option (4) sodium-22 to neon-22 — Correct for \( \beta^{+} \) decay. A proton in the nucleus changes to a neutron, so the atomic number falls by one while the mass number 22 stays the same, giving neon-22.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Beta Decay – “… In beta-minus decay, a neutron transforms into a proton within the nucleus according to

    \( \displaystyle n \rightarrow p + e^- + \bar{\nu} \qquad (13.24) \)

whereas in beta-plus decay, a proton transforms into neutron (inside the nucleus) via

    \( \displaystyle p \rightarrow n + e^+ + \nu \qquad (13.25) \)”