An element 'Y' emits one $\mathrm{\alpha }$-and two $\mathrm{\beta }$- particles to give 'X'. X and Y are

• isotones

• isobars

• isotopes

• isoelectronics

Consider the following pairs of ions:

I. Sc³⁺ and Ti⁴⁺        II. Mn²⁺ and Fe²⁺

III. Fe²⁺ and Co³⁺    IV. Cu⁺ and Zn²⁺

Among these pairs ofions, isoelectronic pairs would include:

• II, III and IV

• I, III and IV

• I, II and IV

• I, II and III

The line spectrum of He⁺ ion will resemble that of :

• hydrogen atom

• Li⁺ ion

• helium atom

• lithium atom

A body of mass x kg is moving with a velocity of 100 ms^-1. Its de-Broglie wavelength is 6.62 x 10^-35 m. Hence, x is :

[h = 6.62 x 10^-34Js]

• 0.1 Kg

• 0.25 Kg

• 0.15 Kg

• 0.2 Kg

595.

The ccrrect statement with regard to ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_2^{-}$ is :

• both ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_2^{-}$ are equally stable

• both ${\mathrm{H}}_2^{+}$ and ${\mathrm{H}}_2^{-}$ do not exist

• ${\mathrm{H}}_2^{-}$ is more stable than ${\mathrm{H}}_2^{+}$

• ${\mathrm{H}}_2^{+}$ is more stable than ${\mathrm{H}}_2^{-}$

Ionisation potential of hydrogen atom is 13.6 eV. Hydrogen atom in ground state is excited by monochromatic light of energy 12.1 eV. The spectral lines emitted by hydrogen according to Bohr's theory will be

• one

• two

• three

• four

According to Bohr's theory, which of the following correctly represents the variation of energy and radius of an electron in n^th orbit of H-atom?

• E_n $\propto \frac{1}{{\mathrm{n}}^2}$, r $\propto \frac{1}{{\mathrm{n}}^2}$

• E_n $\propto \frac{1}{{\mathrm{n}}^2}$, r $\propto {\mathrm{n}}^2$

• E_n $\propto$n², r $\propto$n²

• E_n $\propto$n, r $\propto \frac{1}{\mathrm{n}}$

The correct set of quantum numbers for the unpaired electron of a chlorine atom is :

• 2 , 0 , 0 , +$\frac{1}{2}$

• 2 , 1 , -1 , +$\frac{1}{2}$

• 3 , 1 , -1 , $\pm \frac{1}{2}$

• 3 , 0 , 0 , $\pm \frac{1}{2}$

Number of electron in one molecule of NH₃ :

• 17

• 34

• 7

• 10

The value of magnetic quantum number for l = 3 :

• 0 , +1 , +2 , +3

• 0 , ± 1 , ± 2 , ± 3

• -1 , -2 , -3

• ± 1 , ± 2 , ± 3