Atoms Class 12 MCQs Questions with Answers
Question 1.
An atom stays in an excited state for about:
(a) 10 micro seconds
(b) 10 milli seconds
(c) 10 nano seconds
(d) 10 seconds
Answer
Answer: (c) 10 nano seconds
Question 2.
The energy equivalent to one atomic mass unit is :
(a) 1.6 × 10-19 J
(b) 6.02 × 1023 J
(c) 9.31 MeV
(d) 931 MeV
Answer
Answer: (d) 931 MeV
Question 3.
Who explained the splitting of special lines in magnetic field?
(a) Zeeman
(b) Bohr
(c) Summerfield
(d) Einstein
Answer
Answer: (a) Zeeman
Question 4.
The mass of a neutron is:
(a) 1.00866 u
(b) 1.0866 u
(c) 1.866 u
(d) 0.1866 u
Answer
Answer: (a) 1.00866 u
Question 5.
Isobars have the same:
(a) A
(b) Z
(c) N
(d) All the above
Answer
Answer: (a) A
Question 6.
Isotones have the same:
(a) A
(b) Z
(c) N
(d) All the above
Answer
Answer: (c) N
Question 7.
Half-life of a substance depends on:
(a) pressure
(b) temperature
(c) density
(d) None of these
Answer
Answer: (d) None of these
Question 8.
The concept of electron spin was introduced by:
(a) Becquerel
(b) Goudsmit
(c) Millikan
(d) Uhlenbeek and Goudsmit
Answer
Answer: (d) Uhlenbeek and Goudsmit
Question 9.
The principle that a quantum orbital cannot be occupied by more than two electrons was given by:
(a) Pauli
(b) Millikan
(c) Hund
(d) None of these
Answer
Answer: (a) Pauli
Question 10.
For ionization of excited Hydrogen atom, the, required energy is:
(a) a little less than 13.6
(b) equal to 13.6
(c) more than 13.6
(d) 3.4 or less
Answer
Answer: (d) 3.4 or less
Question 11.
According to Bohr’s theory of hydrogen atom, the radius r of stationary orbit are related to principal quantum number n as:
(a) rg ∝
(b) rg ∝
(c) rg ∝ n
(d) rg ∝ n²
Answer
Answer: (d) rg ∝ n²
Question 12.
Fg and Fe represents the gravitational and electrostatic force respectively between two electrons situated at some distance the ratio
(a) 9.8
(b) 109
(c) 1042
(d) 10-42
Answer
Answer: (d) 10-42
Question 13.
Artificial radioactivity was discovered by:
(a) Joliot
(b) Becquerel
(c) Pauli
(d) None of these
Answer
Answer: (a) Joliot
Question 14.
P-decay produces:
(a) isobars
(b) isotopes
(c) isotones
(d) All the above
Answer
Answer: (a) isobars
Question 15.
Natural radioactivity was discovered by:
(a) Joliot
(b) Becquerel
(c) Pauli
(d) None of these
Answer
Answer: (b) Becquerel
Question 16.
Transmutation of nuclei was discovered by:
(a) Rutherford
(b) Becquerel
(c) Pauli
(d) None of these
Answer
Answer: (a) Rutherford
Question 17.
The energy equivalent to mass defect is called :
(a) binding energy
(b) internal energy
(c) external energy
(d) enthalpy
Answer
Answer: (a) binding energy
Question 18.
The total energy that will be released if a nucleus is built from its constituents is called the:
(a) binding energy of the nucleus
(b) binding energy of the solid
(c) binding energy of the atom
(d) None of these
Answer
Answer: (a) binding energy of the nucleus
Question 19.
The binding energy of
(a) 28.3 eV
(b) 28.3 MeV
(c) 28.3 J
(d) 2.83 MeV
Answer
Answer: (b) 28.3 MeV
Question 20.
The binding energy of a deuteron is about:
(a) 2.22 MeV
(b) 2.22 J
(c) 2.22 eV
(d) None of these
Answer
Answer: (a) 2.22 MeV
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