Among the elements from atomic number 1 to 36, the number of elements which have an unpaired electron in their s subshell is

• 2

• 7

• 6

• 9

The energy of electron in the n^th Bohr orbit of H-atom is

• $-\frac{13.6}{{\mathrm{n}}^2} \mathrm{eV}$

• $-\frac{13.6}{\mathrm{n}} \mathrm{eV}$

• $-\frac{13.6}{\mathrm{n}4} \mathrm{eV}$

• $-\frac{13.6}{{\mathrm{n}}^3} \mathrm{eV}$

Consider the following sets of quantum numbers. Which of the following setting is not permissible arrangement of electrons in an atom?

• n = 4; l = 0; m = 0; s = $-\frac{1}{2}$

• n = 5; l = 3; m = 0; s = $+\frac{1}{2}$

• n = 3; l = 2; m = -2; s = $-\frac{1}{2}$

• n = 3; l = 2; m = -3; s = $+\frac{1}{2}$

No two electron can have the same values of ........ quantum numbers.

• one

• two

• three

• four

475.

The compound in which cation is isoelectronic with anion is :

• NaCl

• CsF

• NaI

• K₂S

What is the effect of increasing pressure on the dissociation of PCl₅ according to the equation?

PCl₅ (g) $\rightleftharpoons$ PCl₃ (g) + Cl₂ (g)

• Dissociation decreases

• Dissociation increases

• Dissociation does not change

• None of the above

The ground state term symbol for an electronic state is governed by :

• Heisenberg's principle

• Hund's rule

• Aufbau principle

• Pauli exclusion principle

What is the ratio of mass of an electron to the mass of a proton ?

• 1 : 2

• 1 : 1

• 1 : 1837

• 1 : 3

The number of orbitals present in the shell with n = 4 is:

• 16

• 8

• 18

• 32

The correct set of quantum number for the unpaired electrons of chlorine atoms is

• 2, 1, -1, +1/2

• 2, 0, 0,+ 1/2

• 3, 1, 1, ±1/2

• 3, 0, 0, ±1/2