- Which of the following trends is observed in atomic size across a period?
a) Increases from left to right
b) Decreases from left to right
c) Remains constant
d) Increases then decreases
Answer: b) Decreases from left to right
Explanation: As you move across a period from left to right, atomic size decreases due to the increasing nuclear charge, which pulls electrons closer to the nucleus.
- Which of the following has the greatest electron affinity?
a) Sulfur (S)
b) Oxygen (O)
c) Selenium (Se)
d) Tellurium (Te)
Answer: a) Sulfur (S)
Explanation: Sulfur has a higher electron affinity than oxygen due to reduced electron-electron repulsion in its larger atomic size compared to oxygen.
- Which of the following statements is correct about d-block elements?
a) They typically form only one oxidation state
b) They form colored compounds
c) They do not form complex compounds
d) Their ionization energies decrease across the period
Answer: b) They form colored compounds
Explanation: d-block elements, or transition metals, form colored compounds due to the presence of unpaired d-electrons that absorb light and undergo electronic transitions.
- Which of the following has the smallest ionic radius?
a) K⁺
b) Ca²⁺
c) Cl⁻
d) S²⁻
Answer: b) Ca²⁺
Explanation: Ca²⁺ has a smaller ionic radius compared to K⁺, Cl⁻, and S²⁻ because it has lost two electrons, leading to a smaller, more compact ion.
- Which element is most likely to form an anion?
a) Potassium (K)
b) Magnesium (Mg)
c) Chlorine (Cl)
d) Aluminum (Al)
Answer: c) Chlorine (Cl)
Explanation: Chlorine, being a non-metal with high electronegativity, has a strong tendency to gain an electron and form a negative ion (Cl⁻).
- Which of the following has the lowest electron affinity?
a) Phosphorus (P)
b) Sulfur (S)
c) Oxygen (O)
d) Nitrogen (N)
Answer: d) Nitrogen (N)
Explanation: Nitrogen has a half-filled p-orbital, which makes it relatively stable. It resists gaining an additional electron, giving it a lower electron affinity compared to phosphorus, sulfur, and oxygen.
- Which of the following oxides is acidic?
a) Na₂O
b) MgO
c) CO₂
d) CaO
Answer: c) CO₂
Explanation: CO₂ is a non-metal oxide and reacts with water to form carbonic acid, making it an acidic oxide. The others are basic oxides.
- Which element has the lowest first ionization energy?
a) Fluorine (F)
b) Phosphorus (P)
c) Sodium (Na)
d) Chlorine (Cl)
Answer: c) Sodium (Na)
Explanation: Sodium, being in Group 1, has a low ionization energy compared to the other elements, which are non-metals and have higher ionization energies.
- Which of the following is not a characteristic of alkali metals?
a) High ionization energy
b) Low electronegativity
c) High reactivity with water
d) Forming +1 oxidation states
Answer: a) High ionization energy
Explanation: Alkali metals have low ionization energies, making it easy for them to lose one electron and form +1 oxidation states. They are highly reactive with water.
- Which of the following has the highest melting point?
a) Lithium (Li)
b) Sodium (Na)
c) Potassium (K)
d) Cesium (Cs)
Answer: a) Lithium (Li)
Explanation: Melting points of alkali metals decrease as you move down the group. Lithium, being the smallest alkali metal, has the highest melting point.
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