Periodic Trends — Set 4
Chemistry · आवर्ती प्रवृत्तियां · Questions 31–40 of 50
In the periodic table, lanthanides are placed separately at the bottom because?
Correct Answer: B. They have very similar properties
• **Lanthanide similarity** = Lanthanides are placed separately because they have very similar chemical properties. • **Easier arrangement** — Placing them separately keeps the periodic table compact and readable. • 💡 Wrong-option analysis: A: Not all are radioactive; C: Some were discovered earlier; D: Similarity is the main reason.
Which element forms the maximum number of compounds?
Correct Answer: B. Carbon
• **Carbon versatility** = Carbon forms the maximum number of compounds (over 10 million known). • **Bonding ability** — Its ability to form chains and multiple bonds allows enormous variety. • 💡 Wrong-option analysis: A: Oxygen forms many compounds but fewer; C: Hydrogen forms fewer; D: Nitrogen forms fewer.
What is the relationship between atomic number and position in the periodic table?
Correct Answer: B. Atomic number increases with position
• **Atomic number progression** = Atomic number increases progressively across periods and down groups. • **Ordered arrangement** — This systematic increase reflects the periodic law discovery by Moseley. • 💡 Wrong-option analysis: A: Strong relationship exists; C: Systematic pattern, not random; D: Different in each group.
Which of the following is a synthetic element that does not occur naturally?
Correct Answer: B. Technetium
• **Technetium synthetic** = Technetium is synthetic element not found in nature, created artificially. • **First synthetic** — It was the first artificial element created, produced in cyclotron. • 💡 Wrong-option analysis: A: Uranium occurs naturally; C: Thorium occurs naturally; D: Radium occurs naturally.
The first element to have more than 100 elements in its series was?
Correct Answer: C. Oganesson
• **Oganesson 118** = Oganesson (element 118) is the last official element in the periodic table. • **Complete rows** — It completes the seventh period with 32 elements included. • 💡 Wrong-option analysis: A: Flerovium is 114; B: Livermorium is 116; D: Ununoctium is alternate name.
Which property generally decreases across a period?
Correct Answer: C. Metallic character
• **Metallic decrease** = Metallic character decreases across a period from left to right. • **Metal to nonmetal transition** — Left side has metals, right side has nonmetals and metalloids. • 💡 Wrong-option analysis: A: Nuclear charge increases; B: Atomic radius decreases; D: Shells don't change in a period.
The effective nuclear charge experienced by an electron depends on?
Correct Answer: C. Both nuclear charge and shielding
• **Combined effect** = Effective nuclear charge depends on both nuclear charge and electron shielding. • **Zeff formula** — Zeff = Z - S, where Z is nuclear charge and S is shielding constant. • 💡 Wrong-option analysis: A: Shielding is crucial factor; B: Nuclear charge is also important; D: Atomic mass is irrelevant.
Which trend is opposite for metals and nonmetals in the periodic table?
Correct Answer: D. All of above
• **Opposite trends** = All these properties show opposite trends for metals versus nonmetals. • **Complementary behavior** — As metallic character increases (metals), electronegativity decreases. • 💡 Wrong-option analysis: A: Only one example; B: Only one example; C: Only one example, all three apply.
Which block elements are involved in chemical bonding?
Correct Answer: C. s, p, and d-block
• **Three blocks bonding** = s, p, and d-block elements participate in chemical bonding and form compounds. • **Valence electrons** — These blocks have valence electrons available for bonding. • 💡 Wrong-option analysis: A: p and d also participate; B: s and d also participate; D: s and p also participate.
The first transition series begins with which element?
Correct Answer: A. Scandium
• **Scandium start** = Scandium (atomic number 21) begins the first transition series. • **d-orbitals filling** — It's the first element to start filling d-orbitals in period 4. • 💡 Wrong-option analysis: B: Titanium is second; C: Potassium is before transition; D: Calcium is before transition.