“Periodic Table” MCQ with Answer Explanation.

71. Which of the following elements has the highest atomic number?
    A) Krypton
    B) Rubidium
    C) Strontium
    D) BromineAnswer: C) Strontium

Explanation: Strontium (Sr) has an atomic number of 38, which is higher than Krypton (Kr, 36), Rubidium (Rb, 37), and Bromine (Br, 35).

72. Which of the following elements is a liquid at room temperature?
    A) Mercury
    B) Gallium
    C) Cesium
    D) All of the above
    Answer: D) All of the above

Explanation: Mercury (Hg) is liquid at room temperature. Gallium (Ga) melts just above room temperature, and Cesium (Cs) has a low melting point making it liquid near room temperature under certain conditions.

73. Which of the following elements has the highest electron gain enthalpy?
    A) Oxygen
    B) Sulfur
    C) Chlorine
    D) Fluorine
    Answer: C) Chlorine

Explanation: Chlorine (Cl) has the highest electron gain enthalpy, meaning it releases the most energy when gaining an electron, despite fluorine being more electronegative.

74. Which of the following elements is a solid at room temperature and has metallic properties?
    A) Bromine
    B) Iodine
    C) Mercury
    D) Sodium
    Answer: D) Sodium

Explanation: Sodium (Na) is a solid metal at room temperature, exhibiting typical metallic properties like conductivity and malleability. Mercury is a liquid, bromine is a liquid, and iodine is a solid nonmetal with different properties.

75. Which element has the ground-state electron configuration of [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³?
    A) Bismuth
    B) Polonium
    C) Antimony
    D) Tellurium
    Answer: C) Antimony

Explanation: The electron configuration [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p³ corresponds to Antimony (Sb), which is in Group 15.

76. Which of the following elements has the highest metallic character?
    A) Aluminum
    B) Gallium
    C) Indium
    D) Thallium
    Answer: D) Thallium

Explanation: Metallic character increases down a group. Thallium (Tl) is below Aluminum, Gallium, and Indium, making it the most metallic among them.

77. Which of the following elements is a chalcogen?
    A) Nitrogen
    B) Oxygen
    C) Carbon
    D) Boron
    Answer: B) Oxygen

Explanation: Chalcogens are elements in Group 16, which include Oxygen (O), Sulfur (S), Selenium (Se), etc.

78. Which of the following elements has the largest metallic radius?
    A) Magnesium
    B) Calcium
    C) Strontium
    D) Barium
    Answer: D) Barium

Explanation: Metallic radius increases down a group. Barium (Ba) has the largest metallic radius among the listed elements.

79. Which of the following elements has the highest number of valence electrons?
    A) Boron
    B) Carbon
    C) Nitrogen
    D) Oxygen
    Answer: D) Oxygen

Explanation: Oxygen has six valence electrons, which is the highest among the listed elements (Boron – 3, Carbon – 4, Nitrogen – 5).

80. Which of the following elements is most likely to form a -2 oxidation state?
    A) Sulfur
    B) Phosphorus
    C) Nitrogen
    D) Carbon
    Answer: A) Sulfur

Explanation: Sulfur (S) commonly forms a -2 oxidation state by gaining two electrons, especially in compounds like H₂S and SO₃²⁻.