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Answer the following. (Class 10 Science 2025, Q28B)

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ScienceCBSE Class 10 · Board exam 2025, set 31/5/1 · 3 marks · Short answer

CBSE Class 10 Science 2025: question 28(B)

Set in the CBSE Class 10 board exam of 2025, paper 31/5/1, section C, question 28(B), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q28(B) · 3 marks · Short answerMetals and Non-metals

Answer the following.

  1. (a)

    Show the formation of Aluminium Nitride (AlN) by the transfer of electrons. [At. no. of Al = 13; At. no. of N = 7]

    0 marks
  2. (b)

    "Ionic compounds are solids and are generally brittle and break into pieces when pressure is applied." Give reason to justify the statement.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Write the configurations first; how many electrons must Al lose and N gain to reach an octet?

Hint 2

Ionic solids are held by attraction between oppositely charged ions; think about what happens when layers of ions are pushed out of place.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) Electronic configurations: Al (Z = 13): 2, 8, 3; N (Z = 7): 2, 5.

    1 mark

  2. (a) Al loses its 3 valence electrons to N: and . Both ions now have the octet 2, 8. The electrostatic attraction between them gives , i.e. AlN. (Dot diagram: Al with 3 crosses → arrows to N with 5 dots → [Al]³⁺ [N with 8 electrons]³⁻.)

    1 mark

  3. (b) In ionic compounds the positive and negative ions are held by strong electrostatic (interionic) forces of attraction in a rigid arrangement, so they are solids. When pressure is applied, layers of ions shift, like charges come face to face and repel, so the crystal breaks into pieces; hence they are brittle.

    1 mark

Answer: (a) Al (2,8,3) transfers 3 electrons to N (2,5), giving Al³⁺ and N³⁻, which combine as AlN; (b) strong electrostatic forces between ions make ionic compounds hard, brittle solids.

Where the marks are

  • Configurations of Al (2,8,3) and N (2,5) (½ + ½ mark)
  • Shows transfer of 3 electrons forming Al³⁺ and N³⁻/AlN (½ + ½ mark)
  • Reason: strong electrostatic forces between oppositely charged ions (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Metals and Non-metals, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.