What is uncertainty in velocity of an electron if uncertainty in measurement of position is 50 pm ? $(m_e = 9.1 \times 10^{-31}\text{kg},\ h = 6.63 \times 10^{-34}\text{Js},\ \pi = 3.142)$

What is the number of unpaired electrons present in ground state of Silicon and Chromium, respectively ?

What is the energy of an electron in a hydrogen atom in a stationary state corresponding to n = 2 ?

If the velocity of the electron in Bohr's first orbit is $2.19 \times 10^6\ \text{Ms}^{-1}$, Calculate the de Broglie wavelength associated with it.
$[h = 6.626 \times 10^{-34}\ \text{J s}$ & Mass of electrons $= 9.10938 \times 10^{-31}$ kg $]$