The ions O^2–, F^–, Na⁺, Mg²⁺ and Al³⁺ are isoelectronic. Their ionic radii show

a decrease from O^2– to F^– and then increase from Na⁺ to Al³⁺
a significant increase from O^2– to Al³⁺
a significant decrease from O^2– to Al³⁺
an increase from O^2– to F^– and then decrease from Na⁺ to Al³⁺

Solution

Amongst isoelectronic species, ionic radii of anion is more than that of cations. Further size of anion increase with increase in –ve change and size of cation decrease with increase in +ve charge. Hence ionic radii decreases from O^2– to Al⁺⁺⁺.

In hydrogen atom, energy of first excited state is –3.4 eV. Find out KE of the same orbit of Hydrogen atom

+3.4 eV
+6.8 eV
–13.6 eV
+13.6 eV

Solution

If a proton and α-particle are accelerated through the same potential difference, the ratio of de-Broglie wavelengths λ_p and λ_α is

3
2√2
1
2

Solution

The orbital diagram in which the Aufbau principle is violated is :

If the nitrogen atom has electronic configuration 1s⁷, it would have energy lower than that of the normal ground state configuration 1s²2s²2p³, because the electrons would be closer to the nucleus. Yet 1s⁷ is not observed because it violates.

Heisenberg uncertainty principle
Hund's rule
Pauli exclusion principle
Bohr postulate of stationary orbits

Solution

As per Pauli exclusion principle "no two electrons in the same atom can have all the four quantum number sequal or an orbital cannot contain more than two electrons and it can accommodate two electrons only when their directions of spin are opposite".

The ratio of magnetic moments of Fe(III) and Co(II) is

7 : 3
3 : 7
√7 : √3
√3 : √7

Solution

The size of isoelectronic species C^4–, N^3– and Mg²⁺ is affected by

nuclear charge (Z)
principle quantum number
interelectronic repulsion
None of these

Solution

Because number of protons (nuclear charge) is different while number of electrons is same in isoelectronic species.

The number of nodal planes in a p_x orbital is

one
two
three
zero

Solution

Given : The mass of electron is 9.11 × 10^–31 kg Plank constant is 6.626 × 10^–34Js,the uncertainty involved in the measurement of velocity within a distance of 0.1 Å is

5.79 × 10⁷ ms^–1
5.79 × 10⁸ ms^–1
5.79 × 10⁵ ms^–1
5.79 × 10⁶ ms^–1

Solution

If the shortest wavelength of the spectral line of H-atom in the Lyman series is X,then the longest wavelength of the line in Balmer series of Li²⁺ is

9x
^x⁄₉
^5x⁄₄
^4x⁄₅

Solution

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