📌 CHEMISTRY WAEC 2026 OBJECTIVE - QUESTIONS & ANSWERS --- SECTION A: BASIC CONCEPTS & ATOMIC STRUCTURE Which of the following particles has the smallest mass? A. Proton B. Neutron C. Electron D. Alpha particle ✅ ANSWER: C (Electron mass = 9.11 × 10⁻³¹ kg, much smaller than proton/neutron) The number of protons in an atom of ²⁷₁₃Al is: A. 13 B. 14 C. 27 D. 40 ✅ ANSWER: A (Atomic number = number of protons = 13) Isotopes of an element have the same number of: A. Neutrons B. Protons C. Nucleons D. Mass number ✅ ANSWER: B (Isotopes have same atomic number but different mass numbers) The maximum number of electrons in the M shell is: A. 2 B. 8 C. 18 D. 32 ✅ ANSWER: C (M shell = n=3, capacity = 2n² = 18) Which of the following is a d-block element? A. Sodium B. Chlorine C. Iron D. Calcium ✅ ANSWER: C (Iron is transition metal in d-block) The electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁴ represents: A. Oxygen B. Sulphur C. Chlorine D. Argon ✅ ANSWER: B (Atomic number 16 = Sulphur) Which scientist proposed the planetary model of the atom? A. John Dalton B. J.J. Thomson C. Ernest Rutherford D. Niels Bohr ✅ ANSWER: D (Bohr model has electrons in fixed orbits) The atomic number of an element is the number of: A. Neutrons in the nucleus B. Protons in the nucleus C. Nucleons in the nucleus D. Electrons in the outermost shell ✅ ANSWER: B (Atomic number = number of protons) Which of the following orbitals is spherical in shape? A. s B. p C. d D. f ✅ ANSWER: A (s-orbitals are spherical) The relative atomic mass of chlorine is 35.5 because: A. It has 35 protons and 35.5 neutrons B. It has 35.5 protons C. It is an average of isotopes Cl-35 and Cl-37 D. It contains 17.5 neutrons ✅ ANSWER: C (Chlorine has isotopes ³⁵Cl and ³⁷Cl in 3:1 ratio) --- SECTION B: PERIODIC TABLE & PERIODICITY Which of the following elements has the highest electronegativity? A. Chlorine B. Fluorine C. Oxygen D. Nitrogen ✅ ANSWER: B (Fluorine has highest electronegativity = 4.0) Atomic radius across a period: A. Increases B. Decreases C. Remains constant D. Increases then decreases ✅ ANSWER: B (Increased nuclear pull reduces atomic radius) Which group contains the halogens? A. Group 1 B. Group 2 C. Group 7 D. Group 8 ✅ ANSWER: C (Group 7 elements: F, Cl, Br, I, At) Which of the following is NOT a property of alkali metals? A. Low melting point B. High electronegativity C. React vigorously with water D. Form basic oxides ✅ ANSWER: B (Alkali metals have low electronegativity) The most reactive non-metal in group 7 is: A. Iodine B. Bromine C. Chlorine D. Fluorine ✅ ANSWER: D (Reactivity decreases down group 7) Elements in the same group have the same number of: A. Electron shells B. Valence electrons C. Neutrons D. Protons ✅ ANSWER: B (Same group = same valence electron configuration) Which period contains the first transition series? A. Period 2 B. Period 3 C. Period 4 D. Period 5 ✅ ANSWER: C (Period 4: Sc to Zn)a The oxide of which element is amphoteric? A. Sodium B. Magnesium C. Aluminium D. Silicon ✅ ANSWER: C (Al₂O₃ reacts with both acids and bases) REACT, SHARE AND FORWARD TO EVERYONE ❤️🔥

You're on a roll — I've reviewed your answers for Sections A and B. Most of your answers are correct, along with their explanations. However, there is one correction needed in Section A. Here's the verification: SECTION A: BASIC CONCEPTS & ATOMIC STRUCTURE 1. ✅ Correct. 2. ✅ Correct. 3. ✅ Correct. 4. ✅ Correct. 5. ✅ Correct. 6. ✅ Correct. 7. ❌ Incorrect. The scientist who proposed the planetary model of the atom (where electrons orbit a central nucleus like planets around the sun) was Ernest Rutherford. Niels Bohr later refined this model by introducing the concept of electrons orbiting in fixed, quantized energy levels. The correct answer is C. Ernest Rutherford. 8. ✅ Correct. 9. ✅ Correct. 10. ✅ Correct. SECTION B: PERIODIC TABLE & PERIODICITY 1. ✅ Correct. 2. ✅ Correct. 3. ✅ Correct. 4. ✅ Correct. 5. ✅ Correct. 6. ✅ Correct. 7. ✅ Correct. 8. ✅ Correct. All answers are correct except for A.7. Drop the next question 📸