Which set of elements forms stable,covalently bonded hydrogen-bonded hydrides?

$A$ photon of energy $8\,eV$ is incident on a metal surface of threshold frequency $1.6 \times 10^{15}\,Hz$. The maximum kinetic energy of the emitted photoelectrons is ...............$eV$ $(h = 6.6 \times 10^{-34}\,Js)$.

An atomic power nuclear reactor can deliver $300 \ MW$. The energy released due to the fission of each nucleus of a uranium atom $^{238}U$ is $170 \ MeV$. The number of uranium atoms fissioned per hour will be:

Which of the following is not correct?

$A$ constant torque acting on a uniform circular wheel changes its angular momentum from $A_0$ to $4A_0$ in $4 \ s$. The magnitude of this torque is

An element $P$ has atomic number $56$. What will be the formula of its halide?