75 free MCQs on Structure of Atom, each with its own worked answer and explanation. Explore how electrons are arranged inside an atom. Covers Bohr's model, quantum numbers, Heisenberg's uncertainty principle, shapes of s, p, d orbitals, and electronic configuration rules.
Take the timed Structure of Atom chapterwise test →75 practice questions on Structure of Atom, sorted Easy → Hard. Try each one first, then open its answer page for the worked explanation. Want the full theory first? Read the Structure of Atom notes.
Bohr's model: electrons occupy fixed circular shells (K, L, M) around the nucleus, with each shell holding up to 2n2 electrons.
Q1.
According to Planck's quantum theory, the energy of a photon is directly proportional to its:
Q2.
The photoelectric effect provides experimental evidence for the ... nature of electromagnetic radiation.
Q3.
The Lyman series of the hydrogen emission spectrum is found in which region of the electromagnetic spectrum?
Q4.
The wave (dual) nature of matter, relating wavelength to momentum, was first proposed by:
Q5.
The approximate value of Planck's constant (h) is:
Q6.
The center of an atom is called the:
Q7.
Which subatomic particle has a positive charge?
Q8.
Which subatomic particle has a negative charge?
Q9.
Which subatomic particle has no charge?
Q10.
Atomic number is equal to the number of:
Q11.
Mass number is equal to:
Q12.
In a neutral atom, the number of protons is equal to the number of:
Q13.
Electrons are found mainly in:
Q14.
The first electron shell can hold a maximum of:
Q15.
The second electron shell can hold a maximum of:
Q17.
Most of the mass of an atom is present in the:
Q18.
An atom that gains or loses electrons becomes a:
Q19.
Atoms of the same element always have the same number of:
Q20.
The symbol Z is commonly used for:
Q21.
The subatomic particle that carries a negative charge is the:
Q22.
The maximum number of electrons that the L shell (n = 2) can hold is:
Q23.
Isotopes of an element have the same number of:
Q24.
The mass number of an atom is equal to the number of:
Q25.
Which quantum number describes the shape of an orbital?
Q26.
The energy of a photon of radiation of frequency 5 x 10<sup>14</sup> Hz is (h = 6.6 x 10<sup>-34</sup> J s):
Q27.
If the radius of the first Bohr orbit of hydrogen is 0.529 A, the radius of its third orbit (n = 3) is:
Q28.
When an excited electron in a hydrogen atom falls from n = 4 to n = 1, the maximum number of spectral lines that can be emitted is:
Q29.
According to the (n + l) rule, which of the following orbitals is filled first?
Q30.
For an electron present in a 3d orbital, the number of possible values of the magnetic quantum number (m<sub>l</sub>) is:
Q31.
An atom has atomic number 11 and mass number 23. How many neutrons does it have?
Q32.
Which electronic configuration is correct for sodium, atomic number 11?
Q33.
Which electronic configuration is correct for oxygen, atomic number 8?
Q34.
Isotopes are atoms of the same element with different numbers of:
Q35.
Which pair represents isotopes?
Q36.
The maximum number of electrons in a shell is given by:
Q38.
The valence shell is the:
Q39.
Valence electrons mainly decide an element's:
Q40.
Which scientist proposed that electrons revolve in fixed energy levels?
Q41.
Which scientist discovered the nucleus through the gold foil experiment?
Q42.
Which particle was discovered by J.J. Thomson?
Q43.
Which particle was discovered by James Chadwick?
Q44.
An atom with 17 protons and 18 electrons has what charge?
Q45.
The number of neutrons in chlorine-35 with atomic number 17 is:
Q46.
The maximum number of electrons a d subshell can accommodate is:
Q47.
For the principal quantum number n = 3, the allowed values of the azimuthal quantum number l are:
Q48.
The electronic configuration of the chloride ion (Cl⁻, Z = 17) is the same as that of:
Q49.
According to Hund’s rule, electrons occupy degenerate orbitals:
Q50.
The total number of orbitals present in the n = 2 shell is:
Q51.
In a hydrogen atom the ground-state energy is -13.6 eV. The energy of the electron in the n = 2 level is:
Q52.
The wave number of the first line of the Balmer series (n = 3 to n = 2) of hydrogen is (R<sub>H</sub> = 1.097 x 10<sup>7</sup> m<sup>-1</sup>):
Q53.
The de Broglie wavelength of an electron (mass 9.1 x 10<sup>-31</sup> kg) moving at 2.2 x 10<sup>6</sup> m s<sup>-1</sup> is about (h = 6.6 x 10<sup>-34</sup> J s):
Q54.
Which of the following sets of quantum numbers is allowed for an electron in an atom?
Q55.
The uncertainty in the position of an electron is 1 x 10<sup>-10</sup> m. The minimum uncertainty in its momentum is about (use delta-x times delta-p >= h/4pi, h = 6.6 x 10<sup>-34</sup> J s):
Q56.
Which set of quantum numbers is not possible?
Q57.
Which quantum number mainly determines the shape of an orbital?
Q60.
Which rule says no two electrons in an atom can have the same four quantum numbers?
Q61.
According to Hund's rule, electrons fill equal-energy orbitals by:
Q62.
Which electronic configuration is correct for chlorine, atomic number 17?
Q63.
The number of unpaired electrons in a nitrogen atom, 1s<sup>2</sup> 2s<sup>2</sup> 2p<sup>3</sup>, is:
Q66.
Which isotope of hydrogen has one proton and one neutron?
Q67.
Which isotope of hydrogen has one proton and two neutrons?
Q68.
What is the maximum number of electrons in the N shell?
Q69.
Which principle says the exact position and momentum of an electron cannot both be known exactly?
Q70.
Which orbital is spherical in shape?
Q71.
Using E = −13.6/n² eV for hydrogen, the energy of the n = 2 level is:
Q72.
The de Broglie wavelength of a particle is inversely proportional to its:
Q74.
How many electrons in an atom can have the quantum numbers n = 3, l = 2?
Q75.
The Heisenberg uncertainty principle states that one cannot simultaneously know exactly a particle’s position and its:
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