MCQs — Atomic Structure

Practice questions for Chemistry.

Question 21

An atom absorbs a specific amount of energy and an electron jumps from a lower energy level to a higher one. Which atomic model best explains this behaviour?

A. Dalton's atomic model

B. Thomson's model

C. The plum pudding model

D. Bohr's atomic model

Question 22

Why can Dalton's model not explain how an atom of the same element can have different masses (isotopes)?

A. Dalton's model already fully explained isotopes

B. Dalton's model was based on the existence of neutrons

C. Dalton assumed all atoms of an element were identical in mass, with no allowance for varying numbers of neutrons

D. Isotopes were not discovered by scientists

Question 23

Which scientist proposed that atoms are mostly empty space with a small, dense, positively charged nucleus?

A. Rutherford

B. Dalton

C. Bohr

D. Heisenberg

Question 24

Which scientist introduced the idea of fixed, quantized energy levels for electrons?

A. Dalton

B. Bohr

C. Rutherford

D. Heisenberg

Question 25

How does the modern (quantum mechanical) view of atomic structure differ from Dalton's original idea of the atom?

A. The modern view says atoms cannot be divided, exactly like Dalton believed

B. Dalton's model already included the nucleus and electrons

C. There is no real difference between the two views

D. The modern view describes atoms as containing a nucleus, subatomic particles and probability-based electron regions, while Dalton viewed atoms as solid, indivisible spheres

Question 26

The scattering of most alpha particles straight through gold foil, with very few deflected, mainly supported the conclusion that:

A. Atoms are mostly empty space with a tiny, dense nucleus

B. Atoms have no internal structure at all

C. Electrons are located inside the nucleus

D. The atom has no positive charge anywhere

Question 27

Why did classical physics predict that Rutherford's model of the atom would be unstable?

A. Classical physics predicted atoms have no electrons

B. Orbiting electrons, according to classical physics, should continuously lose energy as radiation and spiral into the nucleus

C. Classical physics predicted the nucleus would repel all electrons away

D. Classical physics predicted atoms could never form

Question 28

Bohr's atomic model successfully explained the line spectrum observed for which element?

A. Helium

B. Lithium

C. Hydrogen

D. Carbon

Question 29

A scientist tries to determine both the exact position and exact speed of an electron in an atom at the same instant but finds this impossible to do with certainty. This situation is best explained by:

A. The Heisenberg Uncertainty Principle

B. Dalton's atomic theory

C. Rutherford's nuclear model

D. The law of conservation of mass

Question 30

Why is the quantum mechanical model considered a more accurate description of the atom than Bohr's model?

A. It removes the nucleus from atomic structure entirely

B. It assumes electrons are stationary particles

C. It denies that electrons exist

D. It accounts for the wave nature of electrons and the uncertainty in determining their exact position

Question 31

The subatomic particle that carries a positive charge is the:

A. Neutron

B. Electron

C. Proton

D. Photon

Question 32

The subatomic particle that carries no electric charge is the:

A. Proton

B. Neutron

C. Electron

D. Ion

Question 33

The subatomic particle that carries a negative charge is the:

A. Proton

B. Neutron

C. Electron

D. Nucleon

Question 34

Compared to a proton, the relative mass of an electron is:

A. Exactly the same

B. Much smaller (about 1/1836 of a proton's mass)

C. Much larger

D. Twice as large

Question 35

Protons and neutrons have approximately:

A. The same relative mass as each other, about 1 atomic mass unit each

B. Very different masses from each other

C. No measurable mass at all

D. Mass equal to that of an electron

Question 36

Protons and neutrons are located in which part of the atom?

A. The outer shells

B. Outside the atom entirely

C. In orbitals far from the atom

D. The nucleus

Question 37

Electrons are located:

A. In shells or orbitals surrounding the nucleus

B. Inside the nucleus with protons

C. Inside the nucleus with neutrons

D. Completely outside the atom's structure

Question 38

In a neutral atom, how does the number of electrons relate to the number of protons?

A. Electrons always outnumber protons by one

B. Protons always outnumber electrons by one

C. There is no fixed relationship between them

D. They are equal, so the positive and negative charges balance out

Question 39

When a beam of protons, neutrons and electrons passes through an electric field, the protons are deflected toward the negative plate, the electrons toward the positive plate, and the neutrons pass straight through undeflected. Why does this happen?

A. Because all three particles carry the same charge

B. Because protons are positively charged, electrons are negatively charged, and neutrons carry no charge

C. Because neutrons are heavier than protons

D. Because protons and electrons are identical particles

Question 40

An atom in which the number of protons equals the number of electrons is described as:

A. Positively charged

B. Negatively charged

C. Electrically neutral

D. Radioactive

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