Neutron decay in free space is given as follows:
$_0n^1 \to _1H^1 + _{-1}e^0 + [\,\,]$
Then the particle in the bracket is:

Find the $Q$-value and the kinetic energy of the emitted $\alpha$-particle in the $\alpha$-decay of $(a) \; ^{226}_{88} Ra$ and $(b) \; ^{220}_{86} Rn$.
Given:
$m(^{226}_{88} Ra) = 226.02540 \; u$
$m(^{222}_{86} Rn) = 222.01750 \; u$
$m(^{220}_{86} Rn) = 220.01137 \; u$
$m(^{216}_{84} Po) = 216.00189 \; u$
$m(^{4}_{2} He) = 4.002603 \; u$

$A$ radioactive substance emits

$A$ radioactive reaction is $_{92}U^{238} \to _{82}Pb^{206}$. How many $\alpha$ and $\beta$ particles are emitted?

At a particular instant,the emissions from a radioactive compound are deflected in a magnetic field. The compound could be emitting which of the following at that instant?
$(i)$ Electrons $(ii)$ Protons $(iii)$ $He^{+2}$ particles $(iv)$ Neutrons

$A$ radioactive nucleus is initially at rest. It decays by emitting an electron and a neutrino at right angles to each other. The momentum of the electron is $3.2 \times 10^{-23} \ kg \cdot m/s$ and the momentum of the neutrino is $6.4 \times 10^{-23} \ kg \cdot m/s$. What is the direction of the recoil of the nucleus with respect to the direction of the electron?