Chemistry Past Paper PDF - Atomic Structure - JEE Mains

## MAINS SOLVING-I ### Subject: Chemistry ### Topic: Atomic Structure #### SINGLE CORRECT OPTION 1. Henry Moseley studied characteristics X-ray spectra of elements. The graph which represents his observation correctly is (Given v = Frequency of X-ray emitted, Z = atomic number) [April 08, 2023 (1...

## MAINS SOLVING-I ### Subject: Chemistry ### Topic: Atomic Structure #### SINGLE CORRECT OPTION 1. Henry Moseley studied characteristics X-ray spectra of elements. The graph which represents his observation correctly is (Given v = Frequency of X-ray emitted, Z = atomic number) [April 08, 2023 (110)] a) $\sqrt{v}$ b) $v$ c) $v^2$ d) $\frac{v}{Z}$ 2. Given below are two statements, one is labelled as assertion and the other is labelled as reason. [April 06, 2023 (1)] **Assertion:** Loss of electron from hydrogen atom results in a nucleus of -1.5×10 pm size. **Reason:** Proton (H+) always exists in combined form. In the light of the above statements, choose the most appropriate answer from the options given below: a) Both A and R are correct, R is the correct explanation of A b) A is correct but R is not correct c) A is not correct but R is correct d) Both A and R are correct but R is NOT correct explanation of A 3. Which one of the following sets of ions represents a collection of isoelectronic species? (Given: Atomic number: F:9, Cl: 17, Na:11, Mg:12, Al:13, K:19, Ca:20, Sc:21) [Feb. 01, 2023 (0)] a) $N^{-3}, O^{-2}, F^{-}, S^{-2}$ b) $Ba^{+2}, Sr^{+2}, K^{+}, Ca^{+2}$ c) $K^{+}, Cr, Ca^{+2}, Sc^{+3}$ d) $Li, Na, Mg^{+2}, Ca^{+2}$ 4. It is observed that characteristic X-ray spectra of elements show regularity. When frequency to the power ‘n’ i.e. $v^n$ of X-rays emitted is plotted against atomic number ‘Z’, following graph is obtained. [Jan. 24, 2023 (11)] 5. Hydrogen has three isotopes: protium (H), deuterium (2H or D) and tritium (3H or T). They have nearly the same chemical properties but different physical properties. They differ in a) number of protons b) atomic number c) electronic configuration d) atomic mass [June 28, 2022 (II)] 6. The minimum energy that must be possessed by photons in order to produce the photoelectric effect with platinum metal is: [June 25, 2022 (II)] Given: The threshold frequency of platinum is 1.3×10¹⁵ s^-1 and ℎ=6.6×10^-34 Js. a) 8.58×10^-19 J b) 6.24×10^-16 J c) 3.21×10^-18 J d) 9.76×10^-20 J 7. The energy of an electron in the first Bohr orbit of hydrogen atom is -2.18×10^-18 J. Its energy in the third Bohr orbit is [April 13, 2023 (13)] a) $\frac{1}{27}$ of this value b) One third of this value c) Three times of this value d) $\frac{1}{9}$ of this value 8. Which transition in the hydrogen spectrum would have the same wavelength as the Balmer type transition from n=4 to n=2 of He spectrum? a) n=2 to n=1 b) n=4 to n=3 c) n=1 to n=2 d) n=3 to n=4 [Jan. 31, 2023 (II)] 9. The shortest wavelength of hydrogen atom in Lyman series is λ. The longest wavelength in Balmer series of He+ is [Jan. 29, 2023 (II)] a) $\frac{9λ}{4}$ b) $\frac{λ}{2}$ c) $\frac{36λ}{5}$ d) $\frac{5λ}{9}$ 10. The radius of the $2^{nd}$ orbit of $Li^{+2}$ is $x$. The expected radius of the $3^{rd}$ orbit of $Be^{+3}$ is: [Jan. 25, 2023 (II)] a) $\frac{4}{9}x$ b) $\frac{141}{16}x$ c) $\frac{16}{27}x$ d) $\frac{27}{16}x$ #### NUMERICAL TYPE QUESTIONS 46. The energy of one mole of photons of radiation frequency 2×1014 Hz in J mol^-1 is _________. (Nearest integer) (Given: ℎ=6.626×10^-34 Js, NA =6.022×10²³ mol^-1) [NV, April 24, 2023 (II)] 47. The total number of isoelectronic species from the given set is ___________. [April 06, 2023 (II)] 48. The number of incorrect statements about the black body from the following is ___________. [NV, April 10, 2023 (II)] a) Emit or absorb energy in the form of electromagnetic radiation b) Frequency distribution of the emitted radiation depends on temperature c) At a given temperature, intensity vs frequency curve passes through a maximum value d) The maximum of the intensity vs frequency curve is at a higher frequency at higher temperature compared to that at lower temperature. 49. The electron in the $n^{th}$ orbit of $Li^{+2}$ is excited to (n+ 1)^th using radiation of energy 1.47×10^-17 J (as shown in the diagram). The value of n is _________. Given: R = 2.18×10^-18 J. [NV, April 10, 2023 (II)] 50. The number of following statements which are Incorrect is ___________. [NV, January 30, 2023 (II)] a) Line emission spectra are used to study the electronic structure b) The emission spectra of atoms in the gas phase show a continuous spread of wavelengths from red to violet c) An absorption spectrum is like the photographic negative of an emission spectrum d) The element helium was discovered in the sun by spectroscopic method. 51. Assume that the radius of the first Bohr orbit of hydrogen atom is 0.5 A°. The radius of the third Bohr orbit of He+ is _________ picometer (Nearest Integer) [NV, January 29, 2023 (II)]