MCQs — Atomic Structure

Practice questions for Chemistry.

← Back to Atomic Structure

Question 121

A positively charged ion, formed when an atom loses one or more electrons, is called a:

A. Anion

B. Isotope

C. Neutron

D. Cation

Question 122

A negatively charged ion, formed when an atom gains one or more electrons, is called an:

A. Cation

B. Isotope

C. Anion

D. Proton

Question 123

Why does an atom become positively charged when it loses electrons?

A. Because it then has more protons (positive charges) than electrons (negative charges)

B. Because it gains extra protons when it loses electrons

C. Because losing electrons removes all its protons

D. Because electrons carry a positive charge

Question 124

Why does an atom become negatively charged when it gains electrons?

A. Because it loses protons when it gains electrons

B. Because it then has more electrons (negative charges) than protons (positive charges)

C. Because electrons carry a positive charge

D. Because gaining electrons removes neutrons

Question 125

A sodium atom loses one electron to form which ion?

A. Na-

B. Na2+

C. Na2-

D. Na+

Question 126

A magnesium atom loses two electrons to form which ion?

A. Mg2+

B. Mg+

C. Mg2-

D. Mg-

Question 127

An oxygen atom gains two electrons to form which ion?

A. O2+

B. O2-

C. O+

D. O-

Question 128

A fluorine atom gains one electron to form which ion?

A. F+

B. F2-

C. F-

D. F2+

Question 129

How does the formation of a cation differ from the formation of an anion?

A. A cation forms when an atom loses electrons, while an anion forms when an atom gains electrons

B. A cation forms when an atom gains electrons, while an anion forms when an atom loses electrons

C. Both cations and anions form only by losing electrons

D. Both cations and anions form only by gaining electrons

Question 130

When an atom forms an ion, which subatomic particle's number changes while protons and neutrons remain the same?

A. Protons

B. Neutrons

C. Nucleons

D. Electrons

Question 131

An atom of calcium loses two electrons. What is the resulting ion's charge and symbol?

A. 2- charge, written as Ca2-

B. 1+ charge, written as Ca+

C. 2+ charge, written as Ca2+

D. No charge, written as Ca

Question 132

An atom of chlorine gains one electron. What is the resulting ion's charge and symbol?

A. 1+ charge, written as Cl+

B. 1- charge, written as Cl-

C. 2- charge, written as Cl2-

D. No charge, written as Cl

Question 133

Why do metals such as sodium and magnesium typically form cations rather than anions?

A. They tend to gain many extra electrons easily

B. Metals never have any electrons to lose

C. They tend to lose their outer electrons easily to achieve a stable electron arrangement

D. Metals always have a negative charge by default

Question 134

Why do non-metals such as oxygen and fluorine typically form anions rather than cations?

A. They tend to lose many electrons easily

B. They tend to gain electrons easily to achieve a stable electron arrangement

C. Non-metals never have any electrons at all

D. Non-metals always have a positive charge by default

Question 135

Compared to its neutral atom, a cation has:

A. Fewer electrons and the same number of protons

B. More electrons and the same number of protons

C. The same number of electrons and protons

D. Fewer protons and the same number of electrons

Question 136

Compared to its neutral atom, an anion has:

A. Fewer electrons and the same number of protons

B. The same number of electrons and protons

C. Fewer protons and the same number of electrons

D. More electrons and the same number of protons

Question 137

An ion is found to have 11 protons but only 10 electrons. What type of ion is this, and what is its charge?

A. A cation, with a charge of 1+

B. An anion, with a charge of 1-

C. A cation, with a charge of 1-

D. An anion, with a charge of 1+

Question 138

An ion is found to have 8 protons but 10 electrons. What type of ion is this, and what is its charge?

A. A cation, with a charge of 2+

B. An anion, with a charge of 2+

C. A cation, with a charge of 2-

D. An anion, with a charge of 2-

Question 139

Why do the overall properties (such as reactivity) of an ion differ from those of its parent atom?

A. Ions have a completely different number of protons than their parent atom

B. Gaining or losing electrons changes the atom's outer electron arrangement, which determines chemical behaviour

C. Ions and atoms always behave identically

D. Ions have no electrons at all

Question 140

Which of the following correctly pairs an ion with how it is formed?

A. O2- is formed by an oxygen atom losing two electrons

B. Na+ is formed by a sodium atom gaining one electron

C. Mg2+ is formed by a magnesium atom losing two electrons

D. F- is formed by a fluorine atom losing one electron

🎯 How to get the most out of these questions

Attempt each question before revealing the answer.
Read the explanation even when you answered correctly — it reinforces the concept.
Note down any question you got wrong and revisit it the next day.
Use the pagination below the list to work through every page — do not stop at page 1.

📌 MCQs — FAQs

Are answers included for every question in this section?

Yes — each published question includes an answer. Explanations are shown where they have been added.

Can I print these questions?

Yes — use your browser's print option (Ctrl+P / Cmd+P) to print or save the page as PDF.

How often are questions updated?

New questions are added regularly. If a paper pattern changes, existing questions are reviewed and updated.