A radioactive nucleus M undergoes series of decays given below:

$M \overset{\beta ^- \text{decay}}{\longrightarrow}N \overset{\gamma \text{ decay}}{\longrightarrow} O \overset{\alpha \text { decay }}{\longrightarrow} P$

The mass number of M is 150 and Atomic No of M is 64 . The Atomic number of P is

63

The correct answer is Option (3) → 63

In $β^-$ decay, a neutron is converted into a proton, and an electron along with an antineutrino is emitted. This increases the atomic number by 1 but keeps the mass number unchanged.

Mass number M = 150

Atomic number of M = 64

After $β^{-1}$ decay,

Mass Number of O = 150 (same as before)

Atomic number of O = 65 (same as before)

After $α$ decay,

Mass number of P = 150 - 4 = 146

Atomic number of P = 65 - 2 = 63