1

### NEET 2017

Which one is the wrong statement ?
A
The uncertainty principle is

$\Delta E \times \Delta t \ge {h \over {4\pi }}$
B
Half filled and fully filled orbitals have greater stability due to greater exchange energy, greater symmetry and more balanced arrangement.
C
The energy of 2s-orbital is less than the energy of 2p-orbital in case of hydrogen like atoms.
D
de-Broglie's wavelength is given by

$\lambda = {h \over {mv}}$, where m = mass of the particle,

v $=$ group velocity of the particle.

## Explanation

In the case of hydrogen type atoms, energy depends on the principal quantum number only. Therefore 2-s orbital will have energy equal to 2-p orbital.
2

### NEET 2016 Phase 1

Two electrons occupying the same orbital are distinguished by
A
azimuthal quantum number
B
spin quantum number
C
principal quantum number
D
magnetic quantum number

## Explanation

For any two electrons occupying the same orbital values of n, l and ml are same but ms is different [ + $1 \over 2$ and - $1 \over 2$]
3

### NEET 2016 Phase 2

Which of the following pairs of d-orbitals will have electron density along the axes ?
A
${d_{{z^2}}},\,\,{d_{xz}}$
B
dxz,  ${d_{yz}}$
C
${d_{{z^2}}},\,\,{d_{{x^2} - {y^2}}}$
D
${d_{xy}},\,{d_{{x^2} - {y^2}}}$

## Explanation

dx2 - y2 and dz2 orbitals have electron density along the axes.
4

### NEET 2016 Phase 2

How many electrons can fit in the orbital for which n = 3 and $l$ = 1?
A
2
B
6
C
10
D
14

## Explanation

For n = 3 and l = 1, the subshell is 3p and a particular 3p orbital can accodomodate only 2 electrons.