# MCQ | Atomic Structure

QUIZ TEST – I

Question:1. If the electronic structure of oxygen atom is written as 1s2 2s2 2p4 it would violate

(A) Hund’s rule

(B) Paulis exclusion principle

(C) Both Hund’s and Pauli’s principles

(D) None of these

Ans: (D)

Question:2 Number of nodal planes for f-orbital are

(A) 3

(B) 2

(C) 1

(D) 0

Ans: (A)

Question:3. One Bohr magneton equals

(A) $\large \frac{e h c}{4\pi n}$

(B) $\large \frac{e c}{4\pi h m}$

(C) $\large \frac{ h c}{m e^4 \pi}$

(D) $\large \frac{e h }{4\pi m c}$

Ans: (D)

Question:4. Three isotopes of an element have mass numbers M, (M + 1) and (M + 2). If the mean mass number is (M + 0.5) than which of the following ratio may be accepted for M, (M + 1), (M + 2) in that order.

(A) 1 : 1 : 1

(B) 4 : 1 : 1

(C) 3 : 2 : 1

(D) 2 : 1 : 1

Ans: (B)

Question:5.A possible set of quantum numbers for the last electron added to a gallium atom
(Z = 31) in its ground state is

n          l           m         mS

(A)  4          1          –1        +1/2

(B)  4          0          0          –1/2

(C)  3          2          +2        +1/2

(D)  3          0          0          –1/2

Ans: (A)

Question:6. The angle made by angular momentum vector of an electron with z axis is given by

(A) cosθ = l/m

(B) cosθ  = √l/m

(C) $cos\theta = \sqrt{\frac{l+1}{m} }$

(D) $cos\theta = \frac{m}{\sqrt{l(l+1)}}$

Ans: (D)

Question:7. The distance between 3rd and 2nd orbit of hydrogen atom is

(A) 2.646 ×10–8 cm

(B) 2.116 ×10–8 cm

(C) 1.058 ×10–8 cm

(D) 0.529 × 10–8 cm

Ans: (A)

Question:8. An atom has four unpaired electrons. The total spin of this atom will be

(A) 1

(B) 1.5

(C) 2

(D) 4

Ans: (C)

Question:9. For a ‘d’ electron, the orbital angular momentum is

(A) $\sqrt{6 \hbar}$

(B) $\sqrt{2 \hbar}$

(C) $\hbar$

(D) $2 \hbar$

Ans: (A)

Question:10. Which of the following pairs can form correct set of isosters ?

(A) MgS, CaF2

(B) C6H6, B3N3H6

(C) CO, N2O

(D) All the above

Ans: (B)

Question:11. Electromagnetic radiation (Photon) with least wavelength result when an electron in the hydrogen atom falls from n = 5 to
(A) n = 1

(B) n = 2

(C) n = 3

(D) n = 4

Ans: (A)

Question:12. The first five ionization energies of an element are 801, 2428, 3660, 25030, 32835 in kJ/mol. Then the element could be

(A) a halogen

(B) a noble gas

(C) a third group element

(D) a second group element

Ans: (C)

Question:13. The energy required to melt 1 g ice is 33 J. The number of quanta of radiation of frequency 4.67 × 1013 sec–1, that must be absorbed to melt 10 g ice is

(A) 1.065 × 1022

(B) 3.205 × 1023

(C) 9.076 × 1020

(D) none of these

Ans: (A)

Question:14. If the wave length of first line of the Balmer series of hydrogen atom is 656.1 nm, the wave length of second line of this series would be

(A) 218.7 nm

(B) 328.0 nm

(C) 486.0 nm

(D) 640.0 nm

Ans: (C)

Question:15. The energy of an electron in the first Bohr orbit for He+ ion is –54.4 eV. Which one of the following is a possible excited state for electron in Bohr orbit of He+ ion ?

(A) –6.04 eV

(B) – 6.8 eV

(C) – 1.7 eV

(D) +1.36 eV

Ans: (A)

Question:16. The outermost electronic configuration of the most electronegative element is

(A) ns2,np3

(B) ns2,np4

(C) ns2,np5

(D) ns2,np6

Ans: (C)

Question:17. The first four ionization energies of an element are 191, 578,872 and 5962 kcal. The number of valence electrons in the element is

(A) 1

(B) 2

(C) 3

(D) 4

Ans: (C)

Question:18. The quantum numbers of +1/2 and –1/2 for the electron spin represent

(A) Rotation of the electron in clockwise and anticlockwise direction respectively

(B) Rotation of the electron in anticlockwise and clockwise direction respectively

(C) Magnetic moment of the electron pointing up and down respectively

(D) Two quantum mechanical spin states which have no classical analogue.

Ans: (D)

Question:19. A atom forms an ion by the loss of three electrons. The ion has an electronic configuration [Ar]3d6. The symbol of the ion is

(A) Fe3+

(B) Ni3+

(C) Co3+

(D) Mn+3

Ans: (C)

Question:20.  Given that in H–atom, the transition energy for n=1 to n = 2 is 10.2 eV, the energy for the same transition in Be3+ is

(A) 20.4 eV

(B) 30.6 eV

(C) 40.8 eV

(D) None of these