The ratio of the wavelengths of the last lines of the Balmer to Lyman series is

1.	4:1	2.	27:5
3.	3:1	4.	9:4

If the electronic structure of oxygen atom is written as $1{\mathrm{s}}^2, 2{\mathrm{s}}^2$ it would violate:

1.  Hund's rule

2.  Paulis exclusion principle

3.  Both Hund's and Pauli's principles

4.  None of these

The velocity associated with a proton moving at a potential difference of 1000 V is 4.37 × 10⁵ ms^–1. If the hockey ball of mass 0.1 kg is moving with this velocity, then the wavelength associated with this velocity would be:

$1.$ $1.52$ $\times {10}^{-38}$ $\mathrm{m}$
$2.$ $2.54$ $\times$ ${10}^{-32}$ $\mathrm{m}$
$3.$ $1.52$ $\times$ ${10}^{-36}$ $\mathrm{m}$
$4.$ $3.19$ $\times$ ${10}^{-34}$ $\mathrm{m}$

The characteristic velocity associated with a neutron that has a wavelength of 800 pm is :