In the Bohr model of a hydrogen atom, the centripetal force is furnished by the coulomb attraction between the proton and the electron. If $${a_0}$$ is the radius of the ground state orbit, $$m$$ is the mass, $$e$$ is the charge on the electron and $${\varepsilon _0}$$ is the vacuum permittivity, the speed of the electron is
A.
$$0$$
B.
$$\frac{e}{{\sqrt {{\varepsilon _0}{a_0}m} }}$$
C.
$$\frac{e}{{\sqrt {4\pi {\varepsilon _0}{a_0}m} }}$$
D.
$$\frac{{\sqrt {4\pi {\varepsilon _0}{a_0}m} }}{e}$$
An energy of $$24.6\,eV$$ is required to remove one of the electrons from a neutral helium atom. The energy in $$\left( {eV} \right)$$ required to remove both the electrons from a neutral helium atom is
As per Bohr model, the minimum energy (in $$eV$$ ) required to remove an electron from the ground state of doubly ionized $$Li$$ atom $$\left( {Z = 3} \right)$$ is