The melting points and boiling points of some ionic compounds are given below :
Compound Melting Point (K) Boiling Point (K) NaCl 1074 1686 LiCl 887 1600 CaCl2 1045 1900 CaO 2850 3120 MgCl2 981 1685
These compounds are termed ionic because they are formed by the transfer of electrons from a metal to a non-metal. The electron transfer in such compounds is controlled by the electronic configuration of the elements involved. Every element tends to attain a completely filled valence shell of its nearest noble gas or a stable octet.
(i) Show the electron transfer in the formation of magnesium chloride. (1 mark)
(ii) List two properties of ionic compounds other than their high melting and boiling points. (1 mark)
(iii) (A) While forming an ionic compound say sodium chloride how does sodium atom attain its stable configuration ? (2 marks)
OR
(iii) (B) Give reasons : (i) Why do ionic compounds in the solid state not conduct electricity ? (ii) What happens at the cathode when electricity is passed through an aqueous solution of sodium chloride ? (2 marks)
The melting points and boiling points of some ionic compounds are given below :
| Compound | Melting Point (K) | Boiling Point (K) |
|---|---|---|
| NaCl | 1074 | 1686 |
| LiCl | 887 | 1600 |
| CaCl2 | 1045 | 1900 |
| CaO | 2850 | 3120 |
| MgCl2 | 981 | 1685 |
These compounds are termed ionic because they are formed by the transfer of electrons from a metal to a non-metal. The electron transfer in such compounds is controlled by the electronic configuration of the elements involved. Every element tends to attain a completely filled valence shell of its nearest noble gas or a stable octet.
(i) Show the electron transfer in the formation of magnesium chloride. (1 mark)
(ii) List two properties of ionic compounds other than their high melting and boiling points. (1 mark)
(iii) (A) While forming an ionic compound say sodium chloride how does sodium atom attain its stable configuration ? (2 marks)
OR
(iii) (B) Give reasons : (i) Why do ionic compounds in the solid state not conduct electricity ? (ii) What happens at the cathode when electricity is passed through an aqueous solution of sodium chloride ? (2 marks)
(i) The electron transfer in the formation of magnesium chloride is as follows:
Mg (s) Mg2+ (aq) + 2e-
Cl2 (g) + 2e- 2Cl- (aq)
(ii) Two properties of ionic compounds other than their high melting and boiling points are:
- They are soluble in water.
- They conduct electricity when dissolved in water.
(iii) (A) Sodium atom attains its stable configuration by losing one electron to form a positive ion (Na+). This is because sodium has one electron in its outermost shell, which it loses to achieve a stable octet configuration.
OR
(iii) (B) (i) Ionic compounds in the solid state do not conduct electricity because the ions are held together by strong electrostatic forces and are not free to move.
(ii) At the cathode, hydrogen gas is evolved when electricity is passed through an aqueous solution of sodium chloride. This is because water is reduced at the cathode to form hydrogen gas and hydroxide ions.
2H2O (l) + 2e- H2 (g) + 2OH- (aq)
Marking Scheme
- 1(i) 1 mark
- 2(ii) 1 mark
- 3(iii) (A) 2 marks
- 4(iii) (B) 2 marks
Hint
The student should recall the definition of ionic compounds and their properties. They should also understand the concept of electron transfer and how it leads to the formation of ions. The student should be able to apply this knowledge to explain the properties of ionic compounds and the reactions that occur at the cathode.
Quick Oral Answer
Ionic compounds are formed by the transfer of electrons from a metal to a non-metal. The electron transfer in ionic compounds is controlled by the electronic configuration of the elements involved. Ionic compounds have high melting and boiling points, are soluble in water, and conduct electricity when dissolved in water. Sodium atom attains its stable configuration by losing one electron to form a positive ion (Na+). At the cathode, hydrogen gas is evolved when electricity is passed through an aqueous solution of sodium chloride.
Analysis & Explanation
The question requires the student to understand the formation of ionic compounds and their properties. The student needs to show the electron transfer in the formation of magnesium chloride and list two properties of ionic compounds other than their high melting and boiling points. Additionally, the student needs to explain how sodium atom attains its stable configuration and what happens at the cathode when electricity is passed through an aqueous solution of sodium chloride.
Common Mistakes
- 1confusing ionic compounds with covalent compounds
- 2not understanding the concept of electron transfer
- 3not being able to explain the properties of ionic compounds
Interesting Facts
Ionic compounds are formed by the transfer of electrons from a metal to a non-metal.
The electron transfer in ionic compounds is controlled by the electronic configuration of the elements involved.
Spotted a mistake or something unclear?
Tell us — we fix reported answers fast.
Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2023?
This question carries 4 marks in the CBSE Class 10 Science 2023 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 "Ionic Compounds" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2023 paper?
This question appears in Section E in the CBSE Class 10 Science 2023 paper.