Structure of Atom Class 11 MCQ

Answer. (c) Thomson

Explanation: J.J Thomson discovered electrons in 1897 by performing the cathode ray experiment. Electrons are the smallest of the particles that make up an atom, and they carry a negative charge. The number of protons and electrons is equal in a neutral atom.

Answer: a) energy and size of the orbit

Explanation: Among the four quantum numbers, the principal quantum number describes the size and energy of the orbit. It is represented by the symbol “n”. For shells, K, L, M, N, and O, n are given by 1, 2, 3, 4, and 5.

Answer. (c) Helium nucleus

Explanation: Alpha particle consists of two neutrons and two protons and is thus identical to the nucleus of a helium atom. It has no charge. The mass of the particle is approximately the sum of the mass of the proton and neutron. Its charge is equal to that of 2 protons.

Answer: d) 2s

Explanation: As per Aufbau's principle, the orbital or subshell with the lowest energy should be filled first. The ascending order of orbitals energy is given by 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 4f, 5d, 6p, 7s. So 2s orbital should be filled first.

Answer. (b) Valency of an element

Explanation: An element's valence is the number of hydrogen atoms that can combine with or replace (directly or indirectly) one of the element's atoms. Oxygen, for instance, has six valence electrons but its valence is 2. Some elements may have more than one power combination (or valence), while others may have only one.

Answer. (b) Isotopes are the atoms of different elements

Explanation: Isotopes are members of a family of an element that all have the same number of protons but different numbers of neutrons. The number of protons in a nucleus determines the element's atomic number on the Periodic Table.

Answer: a) True

Explanation: Yes, no two electrons have the same set of all four quantum numbers. This is explained by Pauli’s exclusion principle. At most electrons can have all 3 quantum numbers the same as they are in the same orbital. But the spin quantum number’s values are different.

Answer. (a) Chlorine

Answer. (c) Carbon

Explanation: Elements that lose electrons show positive electrovalency and those which gain electrons show negative electrovalency. For example, in the formation of sodium chloride (Na⁺Cl^–), the electrovalency of sodium (Na) is +1, while that of chlorine (Cl) is –1.

Answer: b) Dumbbell

Explanation: The azimuthal quantum number is given by “l”. When l =0, 1, 2, and 3, they are s-orbital, p-orbital, d-orbital, and f-orbital respectively. The shapes of s-orbital, p-orbital, d-orbital, and f-orbital are Spherical, Dumbbell, Double dumbbell, and Complex respectively.

Answer. (b) Neils Bohr

Answer. (b) ₁₈Ar⁴⁰ & ₂₀Ca⁴⁰

Explanation: Isobar is any member of a group of atomic or nuclear species all of which have the same mass number—that is, the same total number of protons and neutrons. Thus, they are isobars.

Answer. (d) Cobalt-60

Explanation: Radioactive elements are made up of atoms whose nuclei are unstable and give off atomic radiation as part of a process of attaining stability. The emission of radiation transforms radioactive atoms into another chemical element, which may be stable or maybe radioactive such that it undergoes further decay.

Answer: d) 0

Explanation: The magnetic quantum of orbital ranges from -( l–1) to l–1. Its symbol is given by m. For 2p orbital, there are 3 magnetic quantum numbers namely -1, 0, and 1. For 2pz orbital it's 0, taking that z is the internuclear axis.

Answer: b) 2

Explanation: Total number of nodes includes angular and radial nodes. Angular nodes and radial nodes are given by the formula n–l -1 and l respectively. So the total number of nodes is n–l -1+l=n–1. For 3d orbit, “n” is 3, so t total number of nodes is 3–1=2.

Answer: b) n=1, l=2, m=0, s=½

Explanation: The set of quantum numbers n=1, l=2, m=0, s=1/2, is not valid because the value of the azimuthal quantum number should lie only in between 0 and n-1, where n is a principal quantum number. So the above set of quantum numbers is not valid.

Answer: c) 32

Explanation: The number of orbitals within an orbit is n2. But as each orbital can accommodate 2 electrons, the number of electrons that can exist with the “n” as the principal quantum number is 2n². So here 2n²=2(4)²=2(16)=32.

Answer: a) 1, 3, 0

Explanation: The representation of the Schrodinger wave function is given by Ψn,l,m. Therefore by comparing Ψn,l,m and Ψ3,1,0 we get that n=3, l=1, and m=0. Here n, l, and m are principal, azimuthal, and magnetic quantum numbers respectively.

Answer: c) Chadwick

Explanation: Chadwick discovered the neutral particles known as neutrons.

Answer: b) 10 electrons

Explanation: n = 6, l = 2, therefore 6d will have 5 orbitals.
Hence maximum of 10 electrons can be accommodated as each orbital can have a maximum of 2 electrons.

Answer: b) -1

Explanation: In the Bohr model, the kinetic energy of an electron in an orbit = + (1/2) (e²/rn)

Total energy of the electron in an orbit = -(e²/2r_n)

Therefore, KE/TE = -1

Answer: c) 3.4 eV

Explanation: For a hydrogen atom, the kinetic energy is the negative of the total energy.
The potential energy is twice the total energy.
The first excited state energy of orbital = -3.4 eV
and kinetic energy of same orbital = -(-3.4 eV) = 3.4 eV
Therefore, the kinetic energy of the same orbit of a hydrogen atom is 3.4 eV.

Answer: d) 9.84 × 10⁵ J mol^-1

Explanation: The energy required when an electron shifts from n = 1 to n = 2

E₂ = −(1.312 × 10⁶ × (1)²)/(2²) = −3.28 × 10⁵ J mol^-1

E₁ = −1.312 × 10⁶ J mol^-1

ΔE = E₂ − E₁

= −3.28 × 10⁵−(−13.2 × 10⁶)

ΔE = 9.84 × 10⁵ J mol^-1

Answer: a) Spin quantum number

Explanation: Electrons having the same orbital are identified by Spin quantum number. Spin Quantum number has two values +1/2 or -½. Spin quantum number explains the direction through which an electron spins in an orbital. An electron in the same orbitals must have opposite spins. 

Answer: d) Chromium

Explanation: As it is in M shell, n = 3

Number of electrons in M shell = 13 → 3s²3p⁶3d⁵

The electronic configuration is (1s²) (2s² 2p⁶) (3s² 3p⁶ 3d⁵) (4s¹)

The element is therefore chromium.

Answer: c) K

Explanation: K = 19 = 1s²2s²2p⁶3s²3p⁶s¹

3s²3p⁶ = m-shell

Hence, k has only 8 electrons in the M shell.

Answer: c) Orientation of orbitals

Explanation: The magnetic quantum number signifies the orientation of orbitals

Answer: d) 743 nm

Explanation: From the Law of Conservation of energy, the energy of the absorbed photon is equal to the combined energy of two emitted photons.
E_T = E₁ + E₂ – (1)

Here, E₁ is the Energy of the first emitted photon emitted and E₂ is the Energy of the second emitted photon.

Now, E = (hc)/ (λ) – (2)

Substituting values from (2) in (1) we get

(hc/λ_T) = (hc)/ (λ₁) + (hc)/ (λ₂)

Therefore, on solving the equation, we get λ₂ = 742.77nm

Answer: d) n, α, p, e

Explanation: The charge to mass ratio (e/m) for the following is as follows –

• neutron, n = (0/1) = 0
• α− particle = (2/4) = 0.5
• Proton, p = (1/1) = 1
• Electron, p = (1/1837) = 1837.

Answer: b) [Kr]4d¹⁰5s¹

Explanation: The electronic configuration of Ag in the ground state is [Kr]4d¹⁰5s¹.

Answer: c) Nuclear model

Explanation: Thomson proposed a model to understand the structure of atom and arrangement of electrons around the nucleus of an atom. It is also known as plum pudding model, raisin pudding model & watermelon model. 

Answer: a) +1.60 X 10^-19

Explanation: The discovery of protons is credited to Rutherford. According to him, protons are positively charged particle present in the structure of an atom. The charge upon single proton is called its absolute charge i.e, +1.60 X 10^-19 C.