- Which of the following halogens has the weakest bond dissociation energy?
a) Fluorine (F₂)
b) Chlorine (Cl₂)
c) Bromine (Br₂)
d) Iodine (I₂)
Answer: a) Fluorine (F₂)
Explanation: Even though fluorine is the smallest and most electronegative halogen, the bond dissociation energy of F₂ is lower than Cl₂ because of the strong electron-electron repulsion in the small F-F bond. As a result, the bond is easier to break compared to chlorine.
- Which of the following has the highest electron affinity?
a) Fluorine (F)
b) Oxygen (O)
c) Chlorine (Cl)
d) Bromine (Br)
Answer: c) Chlorine (Cl)
Explanation: Although fluorine is more electronegative, chlorine has the highest electron affinity. This is because chlorine’s larger size leads to less electron repulsion when an electron is added compared to fluorine, making chlorine more favorable for accepting electrons.
- Which of the following elements is the most metallic?
a) Lithium (Li)
b) Sodium (Na)
c) Potassium (K)
d) Cesium (Cs)
Answer: d) Cesium (Cs)
Explanation: Metallic character increases down the group, so cesium, being the heaviest alkali metal, is the most metallic. Metallic character is related to the ability of an element to lose electrons and form positive ions, which increases as atomic size increases down the group.
- Which of the following trends is observed in the ionization energies of alkali metals?
a) Increases down the group
b) Decreases down the group
c) Remains constant down the group
d) Shows no clear pattern
Answer: b) Decreases down the group
Explanation: As we move down the group in alkali metals, the atomic size increases, which results in a decreased attraction between the nucleus and the outermost electron. Therefore, less energy is required to remove the outermost electron, leading to a decrease in ionization energy.
- Which group in the periodic table contains elements that are all gases at room temperature?
a) Group 1
b) Group 17
c) Group 18
d) Group 2
Answer: c) Group 18
Explanation: Group 18 elements are noble gases, which are all gases at room temperature. These include helium, neon, argon, krypton, xenon, and radon. Their stability is due to their complete outer electron shells, making them chemically inert.
- Which of the following elements has the highest second ionization energy?
a) Sodium (Na)
b) Magnesium (Mg)
c) Aluminum (Al)
d) Silicon (Si)
Answer: a) Sodium (Na)
Explanation: The second ionization energy is the energy required to remove a second electron after the first has been removed. For sodium, after losing one electron, it attains a stable noble gas configuration (Ne). Removing another electron from this stable configuration requires a significantly higher amount of energy compared to the other elements.
- Which of the following elements forms the most basic oxide?
a) Magnesium (Mg)
b) Aluminum (Al)
c) Silicon (Si)
d) Phosphorus (P)
Answer: a) Magnesium (Mg)
Explanation: Basicity of oxides decreases across a period from left to right as metallic character decreases. Magnesium, being an alkaline earth metal, forms a strongly basic oxide (MgO), whereas oxides of aluminum, silicon, and phosphorus are amphoteric or acidic.
- Which of the following has the smallest ionic radius?
a) Na⁺
b) Mg²⁺
c) Al³⁺
d) Si⁴⁺
Answer: d) Si⁴⁺
Explanation: Ionic radius decreases as the charge on the ion increases for a given period. As we move from Na⁺ to Si⁴⁺, the nuclear charge increases, pulling the remaining electrons closer to the nucleus, leading to a smaller ionic radius for Si⁴⁺.
- Which of the following species is the most paramagnetic?
a) F⁻
b) O²⁻
c) N³⁻
d) Na⁺
Answer: b) O²⁻
Explanation: Paramagnetism is associated with the presence of unpaired electrons. Among these species, O²⁻ has unpaired electrons in its p-orbital, making it paramagnetic, while the others have fully paired electrons and are diamagnetic.
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