NIOS Class 10 Science & Technology Chapter 7 Solution

NIOS Class 10 Science & Technology Chapter 7 Solution – Chemical Bonding

NIOS Class 10 Science & Technology Solution Chapter 7 Chemical Bonding. NIOS Class 10 Science & Technology Chapter 7 Question Answers Download PDF. NIOS Class 10 Science Notes.

NIOS Class 10 Science & Technology Chapter 7 Solution

Board NIOS
Class 10th  (Secondary)
Subject Science and Technology (212)
Topic Question Answer, Solution, Notes



(Chemical Bonding)




1) State octet rule.

Ans: – The different elements have the tendency to fill up its octate first and then forming a compound with the other element.


2) Why noble gases are non-reactive?

Ans: – As we all know noble gas has filled up with the electron so there is no possibility to forming a compound by sharing or loosing or accepting of electron.


3)In the table given below three elements and their atomic numbers are given. Which of them are stable and will not form compound?

Ans: – From the table it is clear that there is no such electron in the outer shell which will form any compound with the element of A and B.




1) Name the two types of ions present in NaCl.

Ans: – In this NaCl compound there are two types of ions present in it which are Na (+) and Cl (-).


2)How many shells are present in Na+ ion?

Ans: – Sodium has electronic configuration of (2,8,1) so in Na (+) there is ten electrons so the shell number will be 2 in that case.


3)What is the number of electrons present in Cl– ion?

Ans:- In Cl (-) the shell number will be 3 as the configuration is (2,8,8).


4)Name the type of force of attraction present in ionic compounds.

Ans:- We all know that in a ionic compound there is always an electrostatic force of action is presented.


5)In sodium chloride lattice, how many Cl– ions surround each Na+ ion?

Ans: –  There will be six electron surrounding each Na (+) ion by Cl (-) ions.


6) Show the formation of Na2O, CaCl2 and MgO.

Ans: – 


7) Why NaCl is bad conductor of electricity in solid state?

Ans: – In solid state there will be no such free electron in a NaCl compound. The Na (+) and Cl (-) ion don’t have free electron in its outside shell.




1) How covalent bonds are formed?

Ans: – When there is free electron in the element then there is a one possibility to forming a compound by sharing its electron to the other and making a covalent bond.


2) Show the formation of O2, HCl, Cl2 and N2.

Ans: – 


3)How many covalent bond(s) is/are present in following compounds:

(i) H2O (ii) HCl (iii) O2 (iv) N2.

Ans: – In H2O there is 2 covalent bonds, in HCl there is 1 covalent bond, in O2 there is 2 covalent bonds, in N2 there is 3 covalent bond presents.


4)State loss or gain of electrons (giving their number) in the following changes:

(i) N → N3– (ii) Cl → Cl–

(iii) Cu → Cu2+ (iv) Cr → Cr3+

Ans: – In case (i) electron gain, in case (ii) there is also electron gain, in case (iii) electron are loses and in case (iv) electron are loses.


5) Why ethyl alcohol is bad conductor of electricity in its aqueous solutions?

Ans: – For the conducting of electricity there is needed ions. And in aqueous solution there is no such free ions of H (+) so the conducting of electricity is not possible.




1) Why ionic compounds conduct electricity in aqueous solution?

Ans: – There is free electron in ionic compound which helps for the transferring the electricity between one place to other. As the cation and anion present in ionic compound helps for the conducting of electricity.


2) Covalent compounds have low melting point than an ionic compound why?

Ans: – As we all know the covalent bond are loosely connected by their bond which has low melting point and boiling point. But in ionic compound the bond is strongly connected by the element’s so melting point is high.


3) Explain the formation of Na+ ion from Na atom.

Ans: – The electronic configuration of Na is (2,8,1) and this one electron is losing to form Na (+) and then make the compound.


4) How would you explain the bonding in MgCl2?

Ans: – In magnesium there are 2 free electrons in their last shell and in chlorine there is needed one electron to form the compound so the electron is accepted by chlorine elements to form the compound MgCl2.


5) Which of the following statements are correct for ionic compounds:

(i) They are insoluble in water.

(ii) They are neutral in nature.

(iii)They have high melting points.

Ans: – Option (iii).


6) State three characteristic properties of ionic compounds.

Ans: – The characteristics of ionic compound are –

  • They are strongly connected by ionic bond.
  • They have high melting point.
  • They have low melting point.


7) How does a covalent bond form?

Ans: – The covalent bond is loosely connected by their bond this bind is formed by sharing of electron by each element. This has low melting point and boiling point.


8) What is the number of solvent bonds present in the following molecules?

(i) Cl2 (ii) N2 (iii) O2 (iv) H2.

Ans: – In Cl2 the number of covalent bonds is 2, in N2 the number of covalent bonds is 3 and in O2 the number of covalent bonds is two, in hydrogen the covalent bond is 2.


9) Classify the following statements as true or false:

(i) Ionic compounds contain ions which are held together by weak electro-static forces.

Ans: – False.


(ii) Ionic compounds have high melting and boiling points.

Ans: – True.


(iii) Covalent compounds are good conductors of electricity.

Ans: – False.


(iv) Solid sodium chloride is a good conductor of electricity.

Ans: – False.


10) Classify the following compounds as ionic or covalent:


(i) sodium chloride.

Ans: – Ionic bond.


(ii) calcium chloride

Ans: – Covalent bond.


(iii) oxygen.

Ans: –Covalent bond.


iv) hydrogen chloride.

Ans: – Covalent bond.


v) magnesium oxide

Ans: –Covalent bond.


(vi) nitrogen.

Ans: – Covalent bond.


11)An element ‘X’ has atomic no. 11 and ‘Y’ has atomic no. 8. What type of bond they will form? Write the formula of the compound formed by reacting X and Y.

Ans: – So X is Na or sodium and Y is oxygen or O2. These two elements form the compound N2O by sharing electron or named as covalent bond.


12)Name the type of bonds present in H2O molecule.

Ans: – In hydrogen the covalent bond is present between hydrogen atoms and ionic bond is present between oxygen and hydrogen atoms.

Updated: February 21, 2022 — 12:16 pm

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