Question 93 marksShort AnswerSection A

An element ‘X’ belong to 3rd period and group 13 of the Modern Periodic Table.

(a) Determine the valence electrons and the valency of ‘X’.

(b) Molecular formula of the compound formed when ‘X’ reacts with an element ‘Y’ (atomic number = 8).

(c) Write the name and formula of the compound formed when ‘X’ combines with chlorine.

Metals and Non-metals
Valency and Chemical Formula of Compounds

Official answer

(a) Valence electrons and Valency of 'X': Element 'X' has 33 valence electrons and its valency is 33.


(b) Molecular formula with 'Y' (Oxygen): The molecular formula of the compound formed is X2Y3X_2Y_3 (which corresponds to Aluminium oxide, Al2O3Al_2O_3).


(c) Name and formula with Chlorine: The compound formed is Aluminium chloride and its formula is AlCl3AlCl_3 (or XCl3XCl_3).

Answer keywords:valence electrons 3valency 3X2Y3Al2O3Aluminium chlorideAlCl3

Marking scheme

  1. 1.State that valence electrons = 3 and valency = 3 for element 'X' (1 mark)
  2. 2.Derive the molecular formula X2Y3X_2Y_3 (or Al2O3Al_2O_3) with explanation (1 mark)
  3. 3.State the name as Aluminium chloride and formula as AlCl3AlCl_3 (or XCl3XCl_3) (1 mark)

Hint

Identify element 'X' as Aluminium (AlAl) and element 'Y' as Oxygen (OO). Use the criss-cross method with their respective valencies.

Quick oral answer

Element X is Aluminium. It has 3 valence electrons, a valency of 3, and forms an amphoteric oxide with the formula Al2O3Al_2O_3.

Common mistakes

  1. 1.Writing the formula of the oxide as XY3 instead of X2Y3.
  2. 2.Forgetting to name the compound in part (c) and only writing the formula.

Analysis and explanation

This question connects the periodic classification of elements with the chemical properties of metals from Chapter 3. Aluminium (AlAl) is a key metal discussed in the text, specifically regarding its amphoteric oxide (Al2O3Al_2O_3) and its reaction with oxygen.

Interesting facts

Aluminium oxide (Al2O3Al_2O_3) is amphoteric, meaning it can react with both acids (like HClHCl) and bases (like NaOHNaOH) to produce salt and water. This is a unique property of certain metal oxides!

Question details

Q9 of 36 questions

Board
CBSE
Class
Class 10
Subject
Science
Year
2016
Section
Section A
Marks
3
Type
Short Answer
Chapter
Metals and Non-metals
Topic
Valency and Chemical Formula of Compounds
Bloom's level
Applying
Syllabus topic
Chemical properties of metals, formation of oxides and chlorides

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Frequently asked questions

How many marks does this question carry in CBSE Class 10 Science 2016?

This question carries 3 marks in the CBSE Class 10 Science 2016 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Metals and Non-metals" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Valency and Chemical Formula of Compounds" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2016 paper?

This is a Short Answer question from Section A in the CBSE Class 10 Science 2016 paper.