$A$ radioactive element ${ }_{92}^{242} X$ emits two $\alpha$ particles,one electron and two positrons. The product nucleus is represented by ${ }_{P}^{234} Y$. The value of $P$ is

${ }_{82}^{290} X \xrightarrow{\alpha} Y \xrightarrow{e^{+}} Z \xrightarrow{\beta^{-}} P \xrightarrow{e^{-}} Q$
In the nuclear emission stated above, the mass number and atomic number of the product $Q$ respectively, are

Assertion : The ionising power of $\beta$-particle is less compared to $\alpha$-particles but their penetrating power is more.
Reason : The mass of $\beta$-particle is less than the mass of $\alpha$-particles.

In the emission of $\gamma$-rays from a nucleus:

In a radioactive decay process, the negatively charged emitted $\beta -$ particles are

In the nuclear reaction,${ }_6^{11} C \rightarrow{ }_5^{11} B + \beta^+ + X$,$X$ stands for