AQA Chemistry As Level Paper 1 Exam Questions and answers with
verified Answers (Latest Update 2026) UPDATE!!Detailed Pass
100%:100+ (Multiple choice + short answer format for practice)
SECTION A: ATOMIC STRUCTURE & PERIODICITY
35
Q1. Which number of protons and neutrons is correct for the isotope 17 𝐶𝑙?
• A) 17 protons, 18 neutrons
• B) 17 protons, 35 neutrons
• C) 35 protons, 17 neutrons
• D) 35 protons, 52 neutrons
✅ Answer: A
Rationale: Atomic number (17) = protons. Mass number (35) = protons + neutrons →
neutrons = 35 – 17 = 18.
Q2. What is the electron configuration of a Cr atom (Z=24)?
• A) 1s²2s²2p⁶3s²3p⁶3d⁴4s²
• B) 1s²2s²2p⁶3s²3p⁶3d⁵4s¹
• C) 1s²2s²2p⁶3s²3p⁶3d⁶
• D) 1s²2s²2p⁶3s²3p⁶4s²3d⁴
✅ Answer: B
Rationale: Chromium has a half-filled d-subshell stability exception: [Ar] 3d⁵ 4s¹.
Q3. Which ion is isoelectronic with Ar?
• A) Ca²⁺
• B) Cl⁻
• C) S²⁻
• D) All of the above
✅ Answer: D
Rationale: Ar (18 e⁻). Ca²⁺ (20-2=18), Cl⁻ (17+1=18), S²⁻ (16+2=18).
,Q4. Which orbital has the highest energy in a multi-electron atom?
• A) 3d
• B) 4s
• C) 4p
• D) 3p
✅ Answer: C
Rationale: 4p has higher n+l value than 4s or 3d, and in multi-electron atoms, 4s fills
before 3d but 3d has higher energy once occupied.
Q5. What is the maximum number of electrons that can occupy the 3d subshell?
• A) 2
• B) 6
• C) 10
• D) 14
✅ Answer: C
Rationale: d subshell has 5 orbitals × 2 e⁻ each = 10.
Q6. Which element has the highest first ionisation energy?
• A) Na
• B) Mg
• C) Al
• D) Si
✅ Answer: D
Rationale: Across Period 3, ionisation energy generally increases. Si > Al due to Al losing
an electron from p-subshell (shielding).
Q7. The successive ionisation energies of an element show a large jump after the 2nd
electron. Which group is it in?
• A) Group 1
• B) Group 2
• C) Group 13
• D) Group 14
, ✅ Answer: B
Rationale: Large jump after removing 2 electrons indicates the third electron comes
from a lower energy level (Group 2: ns²).
Q8. Which species has the smallest atomic radius?
• A) Na
• B) Mg
• C) Al
• D) Cl
✅ Answer: D
Rationale: Atomic radius decreases across period; Cl is furthest right.
Q9. Which is the correct order of increasing ionic radius?
• A) Na⁺ < Mg²⁺ < Al³⁺
• B) Al³⁺ < Mg²⁺ < Na⁺
• C) Mg²⁺ < Al³⁺ < Na⁺
• D) Na⁺ < Al³⁺ < Mg²⁺
✅ Answer: B
Rationale: Isoelectronic (10 e⁻): greater nuclear charge → smaller radius.
Q10. Which quantum number describes the shape of an orbital?
• A) n
• B) l
• C) m_l
• D) m_s
✅ Answer: B
Rationale: Azimuthal quantum number (l) defines shape (s,p,d,f).
Q11-15 continue below (abbreviated for space but full exam continues logic). Let me
continue to Q100 in compressed style.
Q11. Which element forms a 3+ ion with electron configuration [Ar]?
• A) Sc
verified Answers (Latest Update 2026) UPDATE!!Detailed Pass
100%:100+ (Multiple choice + short answer format for practice)
SECTION A: ATOMIC STRUCTURE & PERIODICITY
35
Q1. Which number of protons and neutrons is correct for the isotope 17 𝐶𝑙?
• A) 17 protons, 18 neutrons
• B) 17 protons, 35 neutrons
• C) 35 protons, 17 neutrons
• D) 35 protons, 52 neutrons
✅ Answer: A
Rationale: Atomic number (17) = protons. Mass number (35) = protons + neutrons →
neutrons = 35 – 17 = 18.
Q2. What is the electron configuration of a Cr atom (Z=24)?
• A) 1s²2s²2p⁶3s²3p⁶3d⁴4s²
• B) 1s²2s²2p⁶3s²3p⁶3d⁵4s¹
• C) 1s²2s²2p⁶3s²3p⁶3d⁶
• D) 1s²2s²2p⁶3s²3p⁶4s²3d⁴
✅ Answer: B
Rationale: Chromium has a half-filled d-subshell stability exception: [Ar] 3d⁵ 4s¹.
Q3. Which ion is isoelectronic with Ar?
• A) Ca²⁺
• B) Cl⁻
• C) S²⁻
• D) All of the above
✅ Answer: D
Rationale: Ar (18 e⁻). Ca²⁺ (20-2=18), Cl⁻ (17+1=18), S²⁻ (16+2=18).
,Q4. Which orbital has the highest energy in a multi-electron atom?
• A) 3d
• B) 4s
• C) 4p
• D) 3p
✅ Answer: C
Rationale: 4p has higher n+l value than 4s or 3d, and in multi-electron atoms, 4s fills
before 3d but 3d has higher energy once occupied.
Q5. What is the maximum number of electrons that can occupy the 3d subshell?
• A) 2
• B) 6
• C) 10
• D) 14
✅ Answer: C
Rationale: d subshell has 5 orbitals × 2 e⁻ each = 10.
Q6. Which element has the highest first ionisation energy?
• A) Na
• B) Mg
• C) Al
• D) Si
✅ Answer: D
Rationale: Across Period 3, ionisation energy generally increases. Si > Al due to Al losing
an electron from p-subshell (shielding).
Q7. The successive ionisation energies of an element show a large jump after the 2nd
electron. Which group is it in?
• A) Group 1
• B) Group 2
• C) Group 13
• D) Group 14
, ✅ Answer: B
Rationale: Large jump after removing 2 electrons indicates the third electron comes
from a lower energy level (Group 2: ns²).
Q8. Which species has the smallest atomic radius?
• A) Na
• B) Mg
• C) Al
• D) Cl
✅ Answer: D
Rationale: Atomic radius decreases across period; Cl is furthest right.
Q9. Which is the correct order of increasing ionic radius?
• A) Na⁺ < Mg²⁺ < Al³⁺
• B) Al³⁺ < Mg²⁺ < Na⁺
• C) Mg²⁺ < Al³⁺ < Na⁺
• D) Na⁺ < Al³⁺ < Mg²⁺
✅ Answer: B
Rationale: Isoelectronic (10 e⁻): greater nuclear charge → smaller radius.
Q10. Which quantum number describes the shape of an orbital?
• A) n
• B) l
• C) m_l
• D) m_s
✅ Answer: B
Rationale: Azimuthal quantum number (l) defines shape (s,p,d,f).
Q11-15 continue below (abbreviated for space but full exam continues logic). Let me
continue to Q100 in compressed style.
Q11. Which element forms a 3+ ion with electron configuration [Ar]?
• A) Sc
