GCSE Chemistry 2026 — 150 Prac ce
Ques ons with Answers & Ra onales
Section 1: Atomic Structure & the Periodic Table
1. Which particle has a relative charge of +1?
A. Electron
B. Neutron
C. Proton
D. Atom
Answer: C. Proton
Rationale: Protons carry a positive charge of +1, while electrons are −1 and neutrons have no
charge.
2. Which particle has the smallest relative mass?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C. Electron
Rationale: An electron has a relative mass of approximately 1/1836 compared with a proton.
3. What is the atomic number of an element?
A. Number of neutrons
B. Number of protons
C. Number of electrons plus neutrons
D. Number of nucleons
Answer: B. Number of protons
Rationale: Atomic number is defined as the number of protons in the nucleus.
4. What does the mass number represent?
A. Protons only
B. Electrons only
,C. Protons and neutrons
D. Neutrons and electrons
Answer: C. Protons and neutrons
Rationale: The mass number is the total number of protons and neutrons, also called nucleons.
5. Two atoms are isotopes when they have:
A. Different numbers of protons
B. Different numbers of electrons
C. The same number of protons but different numbers of neutrons
D. The same number of neutrons but different numbers of protons
Answer: C. The same number of protons but different numbers of neutrons
Rationale: Isotopes are atoms of the same element, so they have the same proton number but
different neutron numbers.
6. An atom contains 17 protons and 18 neutrons. What is its mass number?
A. 17
B. 18
C. 35
D. 36
Answer: C. 35
Rationale: Mass number = protons + neutrons = 17 + 18 = 35.
7. Which statement about electrons is correct?
A. They are found in the nucleus
B. They have a positive charge
C. They occupy energy levels around the nucleus
D. They determine the mass number
Answer: C. They occupy energy levels around the nucleus
Rationale: Electrons occupy shells or energy levels surrounding the nucleus.
8. Which element has the electron arrangement 2,8,1?
A. Magnesium
B. Sodium
C. Potassium
D. Aluminium
Answer: B. Sodium
Rationale: Sodium has 11 electrons arranged 2,8,1.
,9. Why are noble gases generally unreactive?
A. They have no electrons
B. Their nuclei are unstable
C. They have a full outer electron shell
D. They contain no protons
Answer: C. They have a full outer electron shell
Rationale: A complete outer shell gives noble gases a particularly stable electron arrangement.
10. Which element is in Group 1?
A. Chlorine
B. Oxygen
C. Sodium
D. Neon
Answer: C. Sodium
Rationale: Sodium is an alkali metal and belongs to Group 1.
11. What generally happens to Group 1 reactivity down the group?
A. It decreases
B. It increases
C. It remains constant
D. It becomes zero
Answer: B. It increases
Rationale: The outer electron becomes further from the nucleus and is more easily lost down
Group 1.
12. What generally happens to Group 7 reactivity down the group?
A. It increases
B. It decreases
C. It remains unchanged
D. It becomes radioactive
Answer: B. It decreases
Rationale: Down Group 7, the outer shell is further from the nucleus, reducing the attraction for
an incoming electron.
13. Which element is a halogen?
A. Fluorine
B. Sodium
, C. Calcium
D. Neon
Answer: A. Fluorine
Rationale: Fluorine is a Group 7 halogen.
14. Which element is a noble gas?
A. Chlorine
B. Argon
C. Sulfur
D. Bromine
Answer: B. Argon
Rationale: Argon belongs to Group 0/18, the noble gases.
15. Why did Mendeleev leave gaps in his periodic table?
A. He had run out of elements
B. He expected undiscovered elements to exist
C. He could not measure atomic masses
D. He wanted fewer elements in the table
Answer: B. He expected undiscovered elements to exist
Rationale: Mendeleev deliberately left gaps and used them to predict properties of elements that
had not yet been discovered.
Section 2: Bonding, Structure & Properties
16. Ionic bonding involves:
A. Sharing electrons between metals
B. Transfer of electrons and attraction between oppositely charged ions
C. Sharing protons
D. Transfer of neutrons
Answer: B. Transfer of electrons and attraction between oppositely charged ions
Rationale: Ionic compounds form when electrons are transferred, producing oppositely charged
ions that attract electrostatically.
17. Which pair is most likely to form an ionic compound?
Ques ons with Answers & Ra onales
Section 1: Atomic Structure & the Periodic Table
1. Which particle has a relative charge of +1?
A. Electron
B. Neutron
C. Proton
D. Atom
Answer: C. Proton
Rationale: Protons carry a positive charge of +1, while electrons are −1 and neutrons have no
charge.
2. Which particle has the smallest relative mass?
A. Proton
B. Neutron
C. Electron
D. Nucleus
Answer: C. Electron
Rationale: An electron has a relative mass of approximately 1/1836 compared with a proton.
3. What is the atomic number of an element?
A. Number of neutrons
B. Number of protons
C. Number of electrons plus neutrons
D. Number of nucleons
Answer: B. Number of protons
Rationale: Atomic number is defined as the number of protons in the nucleus.
4. What does the mass number represent?
A. Protons only
B. Electrons only
,C. Protons and neutrons
D. Neutrons and electrons
Answer: C. Protons and neutrons
Rationale: The mass number is the total number of protons and neutrons, also called nucleons.
5. Two atoms are isotopes when they have:
A. Different numbers of protons
B. Different numbers of electrons
C. The same number of protons but different numbers of neutrons
D. The same number of neutrons but different numbers of protons
Answer: C. The same number of protons but different numbers of neutrons
Rationale: Isotopes are atoms of the same element, so they have the same proton number but
different neutron numbers.
6. An atom contains 17 protons and 18 neutrons. What is its mass number?
A. 17
B. 18
C. 35
D. 36
Answer: C. 35
Rationale: Mass number = protons + neutrons = 17 + 18 = 35.
7. Which statement about electrons is correct?
A. They are found in the nucleus
B. They have a positive charge
C. They occupy energy levels around the nucleus
D. They determine the mass number
Answer: C. They occupy energy levels around the nucleus
Rationale: Electrons occupy shells or energy levels surrounding the nucleus.
8. Which element has the electron arrangement 2,8,1?
A. Magnesium
B. Sodium
C. Potassium
D. Aluminium
Answer: B. Sodium
Rationale: Sodium has 11 electrons arranged 2,8,1.
,9. Why are noble gases generally unreactive?
A. They have no electrons
B. Their nuclei are unstable
C. They have a full outer electron shell
D. They contain no protons
Answer: C. They have a full outer electron shell
Rationale: A complete outer shell gives noble gases a particularly stable electron arrangement.
10. Which element is in Group 1?
A. Chlorine
B. Oxygen
C. Sodium
D. Neon
Answer: C. Sodium
Rationale: Sodium is an alkali metal and belongs to Group 1.
11. What generally happens to Group 1 reactivity down the group?
A. It decreases
B. It increases
C. It remains constant
D. It becomes zero
Answer: B. It increases
Rationale: The outer electron becomes further from the nucleus and is more easily lost down
Group 1.
12. What generally happens to Group 7 reactivity down the group?
A. It increases
B. It decreases
C. It remains unchanged
D. It becomes radioactive
Answer: B. It decreases
Rationale: Down Group 7, the outer shell is further from the nucleus, reducing the attraction for
an incoming electron.
13. Which element is a halogen?
A. Fluorine
B. Sodium
, C. Calcium
D. Neon
Answer: A. Fluorine
Rationale: Fluorine is a Group 7 halogen.
14. Which element is a noble gas?
A. Chlorine
B. Argon
C. Sulfur
D. Bromine
Answer: B. Argon
Rationale: Argon belongs to Group 0/18, the noble gases.
15. Why did Mendeleev leave gaps in his periodic table?
A. He had run out of elements
B. He expected undiscovered elements to exist
C. He could not measure atomic masses
D. He wanted fewer elements in the table
Answer: B. He expected undiscovered elements to exist
Rationale: Mendeleev deliberately left gaps and used them to predict properties of elements that
had not yet been discovered.
Section 2: Bonding, Structure & Properties
16. Ionic bonding involves:
A. Sharing electrons between metals
B. Transfer of electrons and attraction between oppositely charged ions
C. Sharing protons
D. Transfer of neutrons
Answer: B. Transfer of electrons and attraction between oppositely charged ions
Rationale: Ionic compounds form when electrons are transferred, producing oppositely charged
ions that attract electrostatically.
17. Which pair is most likely to form an ionic compound?
