IB Physics Structure of the atom Practice Questions

Question 1

The Geiger-Marsden (Rutherford) scattering experiment provided evidence for:

Accepted Answer

A small, dense, positively charged nucleus. Most alpha particles passed straight through, but a few were deflected back, showing the atom has a tiny, dense, positive nucleus.

Question 2

Which particle in the atom carries no net electric charge?

Accepted Answer

Neutron. The neutron is electrically neutral; the proton is positive and the electron negative.

Question 3

In the notation $^{A}_{Z}X$, the quantity $A$ represents the:

Accepted Answer

Number of protons plus neutrons. $A$ is the nucleon (mass) number, the total number of protons and neutrons; $Z$ is the proton number.

Question 4

Isotopes of an element have the same number of protons but different numbers of:

Accepted Answer

Neutrons. Isotopes share the proton number (so are the same element) but have different neutron numbers.

Question 5

Atomic emission spectra consist of discrete lines because:

Accepted Answer

Electrons make transitions between discrete energy levels. Electrons occupy discrete energy levels; transitions between them emit photons of specific energies, giving discrete spectral lines.

Question 6

A neutral atom of $^{12}_{6}	ext{C}$ contains how many electrons?

Accepted Answer

$6$. A neutral atom has equal numbers of protons and electrons. With $Z=6$, it has $6$ electrons.

Question 7

Atoms of the same element with the same number of protons but different numbers of neutrons are called _____.

Accepted Answer

isotopes. Isotopes have identical chemical behaviour but different masses due to differing neutron numbers.

Question 8

The number of protons in a nucleus is called the proton number, also known as the _____ number.

Accepted Answer

atomic. The proton number $Z$ is also called the atomic number and determines the element.

Question 9

An electron in the fourth energy level (E4) of an atom returns to the ground state. Considering all four levels E1 to E4, how many different wavelengths can be emitted?

Accepted Answer

6. The number of distinct downward transitions among 4 levels is 4 choose 2 = 6.

Question 10

A photon is emitted when an electron in an atom moves from a

Accepted Answer

higher to a lower energy level. higher energy level to a lower energy level.

IB Physics: Structure of the atom — Practice Questions & Answers

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