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

Assertion : H₂S is stronger acid than PH₃.

Reason : S is more electronegative than P, conjugate base HS^- is more stable than H₂P^-.

• If both assertion and reason are true and reason is the correct explanation of assertion.

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false.

• If both assertion and reason are false.

346.

If two elements X and Y have 3 and 6 electrons in its outermost shell , then the molecular formula of compound formed by the combination of X and Y :

• XY

• X₃Y

• X₂Y

• X₂Y₃

The probability of finding of three unpaired electron in nitrogen atom is defined by :

• Aufbau's principle

• Uncertainty principle

• Pauli's principle

• Hund's rule

$\mathrm{\alpha }$-particles can be detected by using

• thin aluminium sheet

• barium sulphate

• zinc sulphide screen

• gold foil

In a decay process ${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}$ changes into ${}_{\mathrm{Z}-1}{}^{\mathrm{A}}\mathrm{Y}$. Which process is this?

• $\mathrm{\beta }$-decay

• ${\mathrm{\beta }}^{+}$ decay

• $\mathrm{\alpha }$- decay

• $\mathrm{\gamma }$- decay.

Which of the following pairs represent isotones?

• ${}_{33}{}^{77}\mathrm{As},{}_{34}{}^{ 78}\mathrm{Se}$

• ${}_{78}{}^{195}\mathrm{Pt},{}_{76}{}^{190}\mathrm{Os}$

• ${}_{47}{}^{108}\mathrm{Ag},{}_{48}{}^{112}\mathrm{Cd}$

• ${}_{72}{}^{178}\mathrm{Hf},{}_{56}{}^{137}\mathrm{Ba}$