15 extra multiple-choice questions for p-Block Elements-I (12th Standard Chemistry, Samacheer Kalvi), beyond the ones printed in the textbook — each with the correct option highlighted and a clear, worked explanation. Free to read in English and Tamil.
Q1
What is the general outer electronic configuration of p-block elements?
- A. ns2 np1-6Correct
- B. ns2 np1-5
- C. ns1 np1-6
- D. ns2 np6
Explanation. P-block elements are those where the last electron enters the p orbital. Their valence shell configuration ranges from one to six electrons in the p subshell.
Q2
Which group of p-block elements is specifically referred to as the pnictogens?
- A. Group 13
- B. Group 14
- C. Group 15Correct
- D. Group 16
Explanation. Group 15 elements are known as pnictogens. They include nitrogen and phosphorus, characterized by having five electrons in their outermost valence shell.
Q3
What is the highest possible oxidation state for elements belonging to the boron family (Group 13)?
- A. +1
- B. +2
- C. +3Correct
- D. +4
Explanation. The maximum oxidation state of a p-block group usually equals the total number of valence electrons. Group 13 has three valence electrons, making +3 its highest state.
Q4
Why does boron exhibit non-metallic character while other Group 13 elements are mostly metallic?
- A. Due to its large atomic radius
- B. Due to its very small size and high nuclear chargeCorrect
- C. Because it has low ionisation enthalpy
- D. Due to the absence of valence electrons
Explanation. Boron has a very small atomic radius and a high relative nuclear charge. These specific physical properties prevent it from losing electrons easily, leading to non-metallic behavior.
Q5
How does metallic character generally change when descending a group in the p-block?
- A. It decreases
- B. It increasesCorrect
- C. It remains constant
- D. It first increases then decreases
Explanation. As you move down a group, ionisation energy decreases because the valence electrons are further from the nucleus. This makes it easier to lose electrons, increasing metallic character.
Q6
In Group 13, what trend is observed in electronegativity from boron to aluminium?
- A. It increases significantly
- B. It decreasesCorrect
- C. It remains unchanged
- D. It becomes zero
Explanation. Electronegativity generally decreases down the 13th group from boron to aluminium. This happens because the atomic radius increases, reducing the nucleus's pull on bonding electrons.
Q7
What is responsible for the 'inert pair effect' observed in heavier p-block elements?
- A. The reluctance of outer s-electrons to participate in bondingCorrect
- B. The high reactivity of outer p-electrons
- C. The absence of d-orbitals in the inner shells
- D. The increase in electronegativity down the group
Explanation. In heavier post-transition metals, the outermost s-electrons are more strongly attracted to the nucleus. This makes them less likely to participate in chemical bonding, a phenomenon called the inert pair effect.
Q8
Which of the following elements in Group 14 is classified as a non-metal?
- A. Silicon
- B. Germanium
- C. CarbonCorrect
- D. Tin
Explanation. In Group 14, carbon is the only non-metal. Silicon and germanium are metalloids, while the heavier elements like tin and lead are metals.
Q9
What is the term for the existence of an element in more than one crystalline or molecular form in the same physical state?
- A. Isomerism
- B. AllotropismCorrect
- C. Catenation
- D. Resonance
Explanation. Allotropism refers to the phenomenon where an element exists in multiple structural forms. Carbon, for instance, exists as diamond and graphite, which are its allotropes.
Q10
Which group of elements has the highest ionisation enthalpy in each period?
- A. Group 13
- B. Group 15
- C. Group 17
- D. Group 18Correct
Explanation. Group 18 elements, the inert gases, have completely filled p-orbitals. This stable configuration makes them highly resistant to losing electrons, resulting in the highest ionisation enthalpies.
Q11
Which factor primarily causes the first element of each p-block group to show anomalous behavior?
- A. The presence of vacant d-orbitals
- B. The small size and high electronegativityCorrect
- C. Large atomic radius
- D. Low ionisation enthalpy
Explanation. The first members of p-block groups lack d-orbitals in their valence shell and have the smallest size in their group. These factors contribute significantly to their unique chemical properties.
Q12
Which metal is the most abundant in the earth's crust and belongs to the p-block?
- A. Iron
- B. Copper
- C. AluminiumCorrect
- D. Gold
Explanation. Aluminium is the most abundant metal found in the earth's crust. It is a member of Group 13 and is widely used in various industrial applications.
Q13
Which oxidation state becomes more common in halogens because they tend to gain an electron for stability?
- A. +7
- B. -1Correct
- C. +1
- D. -2
Explanation. Halogens need only one electron to complete their octet and achieve a noble gas configuration. Therefore, they commonly exhibit a -1 oxidation state.
Q14
What general trend is observed regarding ionisation enthalpy when moving from left to right across a period in the p-block?
- A. It generally increasesCorrect
- B. It generally decreases
- C. It remains exactly the same
- D. It shows no predictable pattern
Explanation. As atomic number increases across a period, the effective nuclear charge increases while atomic size decreases. This holds the electrons tighter, requiring more energy for their removal.
Q15
Which sub-block of the periodic table includes a diverse range of metals, non-metals, and metalloids?
- A. s-block
- B. d-block
- C. f-block
- D. p-blockCorrect
Explanation. The p-block is unique because it contains all three types of elements: metals, non-metals, and metalloids. This diversity leads to very varied chemical and physical properties.
Frequently asked questions
How many MCQs are there in p-Block Elements-I?
This chapter has 15 book-back multiple-choice questions, each with the correct answer and a step-by-step explanation.
Are these 12th Standard Chemistry MCQs free to practise online?
Yes. Every question, answer and explanation here is free, and you can also take them as a timed practice test.
Where can I find the p-Block Elements-I book-back answers?
The correct option for each question is highlighted on this page with a worked explanation, plus a quick answer-key summary at the top.
