Structure of Atom MCQ Quiz - Objective Question with Answer for Structure of Atom - Download Free PDF

Last updated on May 30, 2025

The structure of the atom is a fundamental concept in chemistry and physics. It involves understanding the arrangement of subatomic particles, such as protons, neutrons, and electrons, within an atom. The structure of the atom is described by models such as the Bohr model and the quantum mechanical model. MCQs on the structure of the atom cover topics such as atomic models, quantum numbers, electron configurations, periodic table trends, atomic spectra, and atomic properties. These MCQs assess knowledge of atomic structure principles, electron configurations, and periodic table relationships. Check your knowledge on this topic with quick Structure of Atom MCQs for practice.

Latest Structure of Atom MCQ Objective Questions

Structure of Atom Question 1:

Element X forms a chloride with the formula XCl₂, which is a solid with high melting point. X would most likely be in the same group of periodic table as

  1. Na
  2. Al
  3. Mg
  4. K

Answer (Detailed Solution Below)

Option 3 : Mg

Structure of Atom Question 1 Detailed Solution

CONCEPT:

Periodic Groups and Their Properties

  • Elements in the same group of the periodic table have similar chemical properties because they have the same number of valence electrons.
  • Group 2 elements, also known as alkaline earth metals (e.g., Be, Mg, Ca, etc.), typically form compounds with the formula XCl₂, where X is the metal, and Cl is the chloride ion.
  • These chlorides are ionic compounds that are generally solids with high melting points due to the strong electrostatic forces between the ions.

EXPLANATION:

  • The formula of the chloride formed by element X is XCl₂, which suggests that X has a valency of +2.
  • In the periodic table:
    • Na (sodium) belongs to Group 1 and forms NaCl, not XCl₂.
    • Al (aluminum) belongs to Group 13 and forms AlCl₃, not XCl₂.
    • Mg (magnesium) belongs to Group 2 and forms MgCl₂, which matches the formula XCl₂.
    • K (potassium) belongs to Group 1 and forms KCl, not XCl₂.

Since the formula XCl₂ is characteristic of Group 2 elements, X is most likely in the same group as magnesium (Mg).

Therefore, the correct answer is Mg.

Structure of Atom Question 2:

Which one of the following particles in the nucleus of an atom was discovered by J. Chadwick?

  1. Electron
  2. Proton
  3. Positron
  4. Neutron

Answer (Detailed Solution Below)

Option 4 : Neutron

Structure of Atom Question 2 Detailed Solution

CONCEPT:

Discovery of the Neutron

  • In 1932, James Chadwick discovered the neutron, a subatomic particle present in the nucleus of an atom.
  • The neutron is electrically neutral, meaning it has no charge, and its mass is almost equal to that of a proton.
  • Chadwick's discovery was essential in understanding the atomic nucleus and led to advancements in nuclear physics, including nuclear fission and the development of atomic energy.

EXPLANATION:

  • Before Chadwick's discovery, the nucleus of an atom was thought to consist only of protons.
  • However, the atomic mass of many elements was found to be higher than what could be explained by the number of protons alone.
  • Chadwick conducted experiments by bombarding beryllium with alpha particles, which resulted in the emission of a neutral radiation that could not be explained by existing theories.

He concluded that this radiation consisted of previously unknown particles, which he named neutrons.

Therefore, the particle in the nucleus of an atom discovered by J. Chadwick is the neutron.

Structure of Atom Question 3:

The element having tetra-atomic atomicity is ______ .

  1. Helium 
  2. ​Nitrogen 
  3. Phosphorous
  4. Chlorine
  5. None of the above

Answer (Detailed Solution Below)

Option 3 : Phosphorous

Structure of Atom Question 3 Detailed Solution

The correct answer is Phosphorous.

Key Points

  • The present number of atoms in any molecule of an element is called its atomicity.
  • Tetra atomic elements are those which are made up of four atoms
  • Phosphorous exists as molecules made up of four atoms in a tetrahedral structure.
  • Each phosphorus molecule consists of four atoms of phosphorus.

Important Points

  • The following table shows the atomicity of some elements. 
Atomicity of Some Elements 
Name Atomicity
Argon, Helium Monoatomic
Oxygen, Chlorine Diatomic
Nitrogen Diatomic
Phosphorous Tetra – atomic
Sulfur Poly – atomic

Structure of Atom Question 4:

The atomic mass of sulphur is 32 u, and sulphur exists as S₈ molecules. What is the molecular mass of sulphur? 

  1. 256 u
  2. 32 u
  3. 64 u
  4. 128 u

Answer (Detailed Solution Below)

Option 1 : 256 u

Structure of Atom Question 4 Detailed Solution

The correct answer is 256 u.

Key Points

  • The atomic mass of sulphur is 32 u.
  • Sulphur exists as S₈ molecules.
  • To find the molecular mass of sulphur, multiply the atomic mass of sulphur by the number of atoms in one molecule of sulphur.
  • Calculation: 32u×8=256u" id="MathJax-Element-1-Frame" role="presentation" style="position: relative;" tabindex="0">32u×8=256u32u×8=256u
  • Thus, the molecular mass of sulphur is 256 u.

 Additional Information

  • Atomic Mass Unit (u)
    • An atomic mass unit (u) is a standard unit of mass that quantifies mass on an atomic or molecular scale.
    • It is defined as one-twelfth of the mass of an unbound atom of carbon-12 at rest and in its ground state.
  • Molecular Mass
    • The molecular mass (or molecular weight) is the mass of a given molecule and is calculated as the sum of the atomic masses of the atoms in the molecule.
    • It is typically measured in atomic mass units (u).

Structure of Atom Question 5:

Neutrons are present in the nucleus of all atoms, except-

  1. Hydrogen 
  2. Carbon
  3. Oxygen
  4. More than one of the above
  5. None of the above

Answer (Detailed Solution Below)

Option 1 : Hydrogen 

Structure of Atom Question 5 Detailed Solution

The correct answer is Hydrogen.

Key Points

  • Neutrons are present in the nucleus of all atoms, except hydrogen.
  • Hydrogen is the lightest element. 
  • It exists as the stable isotope Deuterium and the unstable, radioactive isotope Tritium.
  • Hydrogen (H) is a colourless, odourless, tasteless, flammable gas.
  • It is the simplest chemical element.
  • The hydrogen has a nucleus consisting of a proton bearing one unit of positive electrical charge, and an electron, bearing one unit of negative electrical charge, is also associated with this nucleus, but no neutron.
  • It exists as a diatomic molecule, H2.

Top Structure of Atom MCQ Objective Questions

Who coined the word ‘atom’?

  1. Democritus
  2. Thomson
  3. E Rutherford
  4. John Dalton

Answer (Detailed Solution Below)

Option 1 : Democritus

Structure of Atom Question 6 Detailed Solution

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  • The word ‘atom’ is coined by Democritus.
  • He suggested that if we go on dividing matter at a certain point the atom becomes indivisible or cannot be divided further.
  • He called these particles as atoms (Indivisible).
  •  

    Scientist

    Discovered

    Thomson

    Electron

    E Rutherford

    Discovered alpha and beta particles

    John Dalton

    Father of Atomic Theory

Alkali metals are assigned which group in the Modern Periodic Table?

  1. Second group
  2. Eighteenth group
  3. Third group
  4. First group

Answer (Detailed Solution Below)

Option 4 : First group

Structure of Atom Question 7 Detailed Solution

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  • Group 1 elements in the Periodic table are known as Alkali metals
  • They have ns1 outermost configuration and belong to the S-block Elements.
  • They also have a strong tendency to donate their valence electrons in the outermost shell to form strong ionic bonds.
  • It contains elements from Lithium (Li) to Francium (Fr).

The element having tetra-atomic atomicity is ______ .

  1. Helium 
  2. ​Nitrogen 
  3. Phosphorous
  4. Chlorine

Answer (Detailed Solution Below)

Option 3 : Phosphorous

Structure of Atom Question 8 Detailed Solution

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The correct answer is Phosphorous.

Key Points

  • The present number of atoms in any molecule of an element is called its atomicity.
  • Tetra atomic elements are those which are made up of four atoms
  • Phosphorous exists as molecules made up of four atoms in a tetrahedral structure.
  • Each phosphorus molecule consists of four atoms of phosphorus.

Important Points

  • The following table shows the atomicity of some elements. 
Atomicity of Some Elements 
Name Atomicity
Argon, Helium Monoatomic
Oxygen, Chlorine Diatomic
Nitrogen Diatomic
Phosphorous Tetra – atomic
Sulfur Poly – atomic

The maximum number of electrons that can be accommodated in M shell is:

  1. 8
  2. 2
  3. 18
  4. 32

Answer (Detailed Solution Below)

Option 3 : 18

Structure of Atom Question 9 Detailed Solution

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  • Electron Shell (also called a Principle energy level) is the region where electrons revolve around the nucleus of an atom.
  • The general formula of filling electron in the shell is 2(n2); where n is the number of the shell.
  • SHELL

    n

    2(n2)

    SHELL MAXIMUM ELECTRON

    K

    1

    = 2(12)

    2

    L

    2

    = 2(22)

    8

    M

    3

    = 2(32)

    18

    N

    4

    = 2(42)

    32

    O

    5

    = 2(52)

    50

Who among the following discovered the neutrons?

  1. J. Chadwick
  2. E. Goldstein
  3. Neils Bohr
  4. Ernest Rutherford

Answer (Detailed Solution Below)

Option 1 : J. Chadwick

Structure of Atom Question 10 Detailed Solution

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The correct answer is J. Chadwick.
Key Points
  • J. Chadwick discovered the presence of neutrons in the nucleus of an atom.
  • An atom is the smallest unit of any chemical element.
  • Atom is made up of electrons, protons, and neutrons.
  • The electron carries a negative charge, proton carries an equal to an electron but a positive charge and a neutron is neutral.
  • Proton and neutrons reside in the nucleus while the electron revolves around the nucleus.

Hence, we can conclude that J. Chadwick discovered neutrons.

Additional Information

Discoverer

Element

J. Chadwick

Neutrons

Ernest Rutherford

Proton

J. J. Thomson

Electron

Eugen Goldstein

positively charged particles in the nucleus

Which of the following elements has the highest electronegativity?

  1. Fluorine
  2. Bromine
  3. Iodine
  4. Chlorine

Answer (Detailed Solution Below)

Option 1 : Fluorine

Structure of Atom Question 11 Detailed Solution

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The correct answer is option 1, i.e. Fluorine.

  • Fluorine is the most electronegative element.
  • As we move right in a period, the electronegativity keeps increasing up to the halogens.
  • This is because the number of electrons keeps increasing in the same valence shell so hold of the nucleus on the electrons is tight.
  • And as we move down in a group, the electronegativity decreases. This is due to the fact that the number of shells keeps increasing down the group so the hold of the nucleus on the valence electron(s) keeps decreasing.
  • Since Flourine is the first member of the halogen family (the rightmost group before noble gases), therefore it is the most electronegative element.

Which of the following is the last element in the Newlands Law of Octaves classification?

  1. Radium
  2. Thorium
  3. Iron
  4. Rhodium

Answer (Detailed Solution Below)

Option 2 : Thorium

Structure of Atom Question 12 Detailed Solution

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  • Newlands Law of Octaves classification attempted to arrange elements by the atomic weight
  • According to Newlands Law of Octaves classification, the eighth element starting from the given one kind is a repetition of the first element in the given kind
  • This is similar to the property of musical notes
  •  The eighth element would have similar atomic weight as that of the first one
  • In this way, Thorium was the last element in the Newlands Law of Octaves classification

To which block do the elements with atomic number 56 belong?

  1. p
  2. f
  3. d
  4. s

Answer (Detailed Solution Below)

Option 4 : s

Structure of Atom Question 13 Detailed Solution

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  • Atomic number 56, Barium belongs to s - block elements.
  • Electronic configuration for the Barium [Xe]6s2
  • Modern Periodic Table is classified into the following elements - p-block, s-block, d-block, and f-block.
  • s-block elements include alkali metals and alkaline earth metals.
  •  

α particles are doubly charged ions of ________.

  1. lithium
  2. beryllium
  3. helium
  4. Hydrogen

Answer (Detailed Solution Below)

Option 3 : helium

Structure of Atom Question 14 Detailed Solution

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The correct answer is helium.

Key Points

  • Alpha Particle
    • α-particles consist of two protons and two neutrons.
    • They are doubly-charged helium ions. Since they have a mass of 4 u, the fast-moving α-particles have considerable energy.
    •  An alpha particle is obtained by removing 2 electrons from a helium atom. So, an alpha particle is a doubly-charged helium ion.
  •  Helium:
    • Helium is a chemical element with the symbol He and atomic number 2.
    • It is a colourless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table.
    •  Its boiling and melting point are the lowest among all the elements.
    • It is the second lightest and most abundant element in the observable universe (hydrogen is the lightest and most abundant).

Additional Information

  • Lithium
    • ​Lithium is a chemical element with the symbol Li and atomic number 3.
    • It is a soft, silver-white metal belonging to the alkali metal group of chemical elements.
  • ​Beryllium
    • Beryllium is very similar to Aluminium.
    • Beryllium is soft and has a low density.
    • It is used in gears and in alloys with copper or nickel.
    • Beryllium is used in Nuclear Reactors.
    • Oxides of Beryllium have a high melting point.
  • Hydrogen
    • Hydrogen was discovered by Henry Cavendish.
    • Hydrogen gas is called as the fuel of the future.
    • Most abundant element in the universe: Hydrogen.
    • Most abundant element on earth's crust: Oxygen
    • Hydrogen is the 'lightest element' in the periodic table.
    • Lithium is the 'lightest metal' in the periodic table.

Who was the first to propose Atomic Theory?

  1. J.J. Thomson
  2. Rutherford
  3. John Dalton
  4. Neils Bohr

Answer (Detailed Solution Below)

Option 3 : John Dalton

Structure of Atom Question 15 Detailed Solution

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The correct answer is option 3, i.e. John Dalton.

Name of the Scientist Discovery
J.J. Thomson Discovered electron, a sub-particle of an atom.
Rutherford an atom is composed of an empty space mostly with electrons orbiting in a set predictable path around a fixed positively charged nucleus(Proton+Neutron).
John Dalton First to propose Atomic Theory
Neils Bohr Atomic structure and the concept of energy of orbits and quantum theory

 

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