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GPAT p-Block Elements (Groups 15-18) — practice questions

Explore 56 free p-Block Elements (Groups 15-18) questions in GPAT Chemistry. Open each question or exercise to read its content, reference answers and available explanation.

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p-Block Elements (Groups 15-18) questions and exercises with answers

Showing questions 1–30 of 56.

The general outer electronic configuration of group 15 elements is:Read the answer and worked solution →Which of the following is **not** a noble gas?Read the answer and worked solution →Among the halogens (F, Cl, Br, I), bond dissociation enthalpy is **lowest** for:Read the answer and worked solution →The **inert pair effect** is most pronounced in:Read the answer and worked solution →Boiling points of hydrogen halides follow which order?Read the answer and worked solution →Which of the following has a **see-saw** molecular geometry around the central atom?Read the answer and worked solution →Order the atomic models as they were proposedRead the answer and worked solution →Match each scientist to their modelRead the answer and worked solution →Match each model to what it could NOT explainRead the answer and worked solution →True or false: Rutherford's modelRead the answer and worked solution →True or false: Bohr's modelRead the answer and worked solution →Complete the reason Bohr's model failsRead the answer and worked solution →Which model does this belong to?Read the answer and worked solution →Match each quantum number to what it is calledRead the answer and worked solution →True or false: the quantum mechanical modelRead the answer and worked solution →Order the structure: from atom down to electronRead the answer and worked solution →Complete the (n + l) ruleRead the answer and worked solution →True or false: orbital energiesRead the answer and worked solution →Match each rule to what it forbids or requiresRead the answer and worked solution →Tap every statement Hund's rule requiresRead the answer and worked solution →The fundamental particlesRead the answer and worked solution →Assertion and reasonRead the answer and worked solution →Two are true, one is notRead the answer and worked solution →Three of these are wrong. Find the one that holds.Read the answer and worked solution →Which principle is being described?Read the answer and worked solution →Flip and pair: symbol with meaningRead the answer and worked solution →Spot the one that does not belongRead the answer and worked solution →Tap every statement true of the Schrodinger modelRead the answer and worked solution →Reading the models backRead the answer and worked solution →Assertion and reason: filling orbitalsRead the answer and worked solution →

Worked practice questions

The general outer electronic configuration of group 15 elements is:

  1. $ns^2 np^2$
  2. $ns^2 np^3$
  3. $ns^2 np^4$
  4. $ns^2 np^5$
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Correct answer: B. $ns^2 np^3$

Group 15 (nitrogen family): N, P, As, Sb, Bi. Outer configuration $ns^2 np^3$, i.e. 5 valence electrons (2 in $s$, 3 in $p$). Group 14: $ns^2 np^2$ (option A — carbon family). Group 16: $ns^2 np^4$ (option C — oxygen family). Group 17: $ns^2 np^5$ (option D — halogens). The half-filled $np^3$ in group 15 gives extra stability (like Cr's half-filled d⁵), making nitrogen unusually unreactive in elemental form.

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Which of the following is **not** a noble gas?

  1. Argon
  2. Krypton
  3. Bromine
  4. Xenon
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Correct answer: C. Bromine

Noble gases (group 18): He, Ne, Ar, Kr, Xe, Rn, Og. All chemically inert in their natural state (Xe and Kr can form a few compounds under extreme conditions). **Bromine** is a halogen (group 17), not a noble gas. It's a reactive non-metal, liquid at room temperature, deep red-brown.

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Among the halogens (F, Cl, Br, I), bond dissociation enthalpy is **lowest** for:

  1. $\mathrm{F_2}$
  2. $\mathrm{Cl_2}$
  3. $\mathrm{Br_2}$
  4. $\mathrm{I_2}$
Show answer and solution

Correct answer: A. $\mathrm{F_2}$

Down group 17: bond enthalpy is Cl-Cl (242) > Br-Br (192) > F-F (158) > I-I (151) kJ/mol approximately. The surprise is **F-F**, which is *lower* than Cl-Cl despite the trend. Two fluorine atoms are very small and the lone pairs on each repel strongly when they bond — that lone-pair repulsion weakens the F-F bond unusually. Flowing down (Cl → Br → I), bond enthalpy decreases steadily as atomic size increases (orbital overlap weakens). The fluorine anomaly explains its outsize reactivity.

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