MCQs — Atomic Structure

Practice questions for Chemistry.

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Question 1

According to Dalton's atomic theory, matter is made up of tiny, indivisible particles called:

A. Molecules

B. Atoms

C. Ions

D. Electrons

Question 2

According to Dalton's atomic theory, atoms of the same element are:

A. Always different in mass

B. Made of different subatomic particles

C. Never able to combine

D. Identical in mass and properties

Question 3

According to Dalton's atomic theory, atoms of different elements combine in:

A. Simple, fixed whole-number ratios to form compounds

B. Random, unfixed ratios

C. Equal amounts only

D. No fixed ratio at all

Question 4

According to Dalton's atomic theory, atoms can be:

A. Freely created during any reaction

B. Destroyed but never created

C. Neither created nor destroyed in a chemical reaction

D. Split into smaller particles easily

Question 5

What is a major limitation of Dalton's atomic theory?

A. It could not explain the existence of subatomic particles, isotopes or ions

B. It correctly predicted the existence of electrons

C. It explained radioactivity in detail

D. It accounted for all types of atoms perfectly

Question 6

Rutherford's atomic model was based on the results of his:

A. Cathode ray tube experiment

B. Photoelectric effect experiment

C. Double-slit experiment

D. Alpha-particle scattering (gold foil) experiment

Question 7

In Rutherford's gold foil experiment, most alpha particles passed straight through the foil, showing that:

A. The atom is a solid, dense sphere

B. Atoms contain no charged particles

C. Most of the atom is empty space

D. Atoms have no nucleus at all

Question 8

In Rutherford's experiment, a small number of alpha particles were deflected at large angles or bounced straight back. What did this indicate?

A. The atom has no nucleus at all

B. The atom has a small, dense, positively charged nucleus

C. Electrons are located in the nucleus

D. The atom is uniformly positive throughout

Question 9

According to Rutherford's model, the electrons of an atom are located:

A. Inside the nucleus with the protons

B. Fixed motionless on the atom's surface

C. Outside the atom entirely

D. Moving around the nucleus in the surrounding space

Question 10

What was a major defect of Rutherford's atomic model?

A. It could not explain the existence of the nucleus

B. It could not explain why orbiting electrons do not lose energy and spiral into the nucleus

C. It predicted atoms have no electrons

D. It could not explain that atoms have mass

Question 11

Bohr's atomic model proposed that electrons move around the nucleus in:

A. Completely random paths that constantly change

B. Straight lines away from the nucleus

C. Fixed circular orbits of specific energy, without radiating energy

D. Orbits inside the nucleus

Question 12

According to Bohr's model, an electron absorbs or emits energy when it:

A. Jumps from one fixed orbit (energy level) to another

B. Remains still within a single orbit

C. Leaves the atom permanently

D. Combines with the nucleus

Question 13

Why was Bohr's atomic model an improvement over Rutherford's model?

A. It proved that atoms have no nucleus

B. It explained why electrons do not spiral into the nucleus by introducing fixed, stable energy levels

C. It disproved the existence of electrons

D. It showed atoms are indivisible

Question 14

The atomic model that describes electrons in terms of probability regions called orbitals, based on the wave nature of electrons, is the:

A. Rutherford's model

B. Dalton's model

C. Thomson's model

D. Quantum mechanical model

Question 15

The principle which states that it is impossible to simultaneously know the exact position and exact momentum of an electron is called the:

A. Heisenberg Uncertainty Principle

B. Aufbau Principle

C. Pauli Exclusion Principle

D. Hund's Rule

Question 16

How does the quantum mechanical model of the atom differ from Bohr's model?

A. It describes electrons as fixed points on the nucleus

B. It removes electrons from the atom entirely

C. It describes electrons as existing in probability regions (orbitals), rather than in fixed, precisely defined orbits

D. It is identical to Bohr's model in every way

Question 17

In modern atomic theory, the small, dense, central part of the atom containing protons and neutrons is called the:

A. Orbital

B. Nucleus

C. Shell

D. Valence region

Question 18

The strong force that holds protons and neutrons together inside the nucleus, overcoming the repulsion between protons, is called the:

A. Nuclear force

B. Gravitational force

C. Electrostatic attraction

D. Magnetic force

Question 19

Why is a nuclear force needed to hold the nucleus together?

A. Because protons and neutrons naturally attract through gravity alone

B. Because electrons hold protons together

C. Because neutrons repel protons

D. Because the positively charged protons would otherwise repel each other and push the nucleus apart

Question 20

A student observes that a beam of alpha particles passes mostly undisturbed through gold foil, but very rarely a particle rebounds almost straight back. Which historical experiment does this describe?

A. Dalton's combination experiment

B. Bohr's spectral line experiment

C. Rutherford's gold foil experiment

D. Heisenberg's uncertainty experiment

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