The wavelength associated with the electron moving in the first orbit of hydrogen atom with velocity $$2.2 \times 10^6 \mathrm{~ms}^{-1}$$ (in nm) is
$$\left(m_e=9.0 \times 10^{-31} \mathrm{~kg}, h=6.6 \times 10^{-34} \mathrm{Js}\right)$$
The energy required (in eV) to excite an electron of H -atom from the ground state to the third state is
An element '$$X$$' with the atomic number 13 forms a complex of the type $$[\mathrm{XCl}(\mathrm{H}_2 \mathrm{O})_5]^{2+}$$. The covalency and oxidation state of $$X$$ in it are respectively
In which of the following oxides of three elements $$X, Y$$ and $$Z$$ are correctly arranged in the increasing order of acidic nature. The electronic configurations of $$X, Y$$ and $$Z$$ are $$[\mathrm{Ne}] 3 s^2 3 p^1, [\mathrm{Ne}] 3 s^2 3 p^5$$. [Ne] $$3 s^2$$ respectively