Chemistry Worksheet Class 11 on Chapter 2 Structure of Atom with Answers - Set 4

The atomic number (Z) is the number of protons in the nucleus; the atomic number defines the element. N represents the number of neutrons in the nucleus. The nucleus’ mass number (A) equals Z + N. The mass number of the nucleus is usually slightly different from its mass in atomic mass units (amu).

Atoms of the same element with different numbers of neutrons are known as isotopes of that element. Hydrogen, for example, has three (3) isotopes: hydrogen-1 (hydrogen), deuterium-2 (deuterium), and hydrogen-3 (deuterium-3) (tritium).

There are currently 118 known elements, which are typically represented on an elemental periodic table. Elements numbered 1 through 98 have all been discovered in nature, whereas elements numbered 99 through 118 have only ever been created artificially.

Download PDF of Class 11 Chemistry Chapter 2 Structure of Atom – Set 4

CBSE Class 11 Chemistry Worksheet Chapter 2 Structure of Atom – Set 4

Q1. The orbital nearest to the nucleus is:

a.) 4f

b.) 5d

c.) 4s

d.) 7p

Q2. The electronic configuration of Cu²⁺ ion is:

a.) [Ar] 3d⁸4s¹

b.) [Ar] 3d⁹4s⁰

c.) [Ar] 3d⁷4s²

d.) [Ar] 3d⁸4s⁰

Q3. What is the maximum number of emission lines obtained when the excited electrons of a hydrogen atom in n = 5 drop to the ground state?

a.) 10

b.) 5

c.) 12

d.) 15

Q4. The maximum number of electrons in a subshell is given by the expression:

a.) 4l – 2

b.) 4l + 2

c.) 2l + 1

d.) 2n²

Q5. In Bohr’s theory, the radius r of the orbit is proportional to ____.

a.) n

b.) n²

c.) n^–1

d.) n^–2

Q6. Symbols ⁷⁹₃₅Br and ⁷⁹ Br can be written, whereas symbols ³⁵₇₉Br and ³⁵Br are not acceptable. Answer briefly.

Q7. List the properties of anode rays.

Q8. What were the observations of Rutherford’s scattering experiment?

Q9. Calculate the wave number of radiations having a frequency of 4 × 10¹¹ kHz.

Q10. What is the experimental evidence in support of the idea that electronic energies in an atom are quantised?

Q11. How many protons, electrons, and neutrons are there in the following nuclei?

i.) ¹⁷₈O

ii.) ²⁵₁₂Mg

iii.) ⁸⁰₃₅Br

Q12. Calculate the kinetic energy of the ejected electron when ultraviolet radiation of frequency 1.6 × 10¹⁵ s^–1 strikes the surface of potassium metal.

[Threshold frequency of potassium metal is 5 × 10¹⁴ s^–1.]

Q13. An atom of an element contains 29 electrons and 35 neutrons. Deduce:

i.) The number of protons

ii.) The electronic configuration of the element

Q14. A hydrogen atom has only one electron, so mutual repulsion between electrons is absent. However, in multielectron atoms, mutual repulsion between the electrons is significant. How does this affect the energy of an electron in the orbitals of the same principal quantum number in multielectron atoms?

Q15. The wavelength of the first spectral line in the Balmer series is 6561 Å. Calculate the wavelength of the second spectral line in the Balmer series.

Q16. Threshold frequency, v_0, is the minimum frequency that a photon must possess to eject an electron from a metal. It is different for different metals. When a photon of frequency 1.0 × 10¹⁵ s^–1 was allowed to hit a metal surface, an electron having 1.988 × 10^–19 J of kinetic energy was emitted. Calculate the threshold frequency of this metal. Show that an electron will not be emitted if a photon with a wavelength equal to 600 nm hits the metal surface.

Q17. According to Bohr’s theory, the electronic energy of a hydrogen atom in the nth Bohr orbit is given by

Calculate the longest wavelength of light that will be needed to remove an electron from the third orbit of the He⁺ ion.

Q18. Differentiate between electromagnetic waves and matter waves.

Q19. If the uncertainty in the position of a moving electron is equal to its de-Broglie wavelength, show that its velocity is completely uncertain.

Q20. Calculate the energy emitted when electrons of 1.0 g atom of hydrogen undergo transition giving the spectral line of largest energy in the visible region of its atomic spectrum. (R_H = 1.1 × 10⁷ m^–1, c = 3 × 10⁸ m s^–1, h = 6.62 × 10^–34 J s)

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• Bohr’s Model of an Atom