WBBSE Class 10 Physical Science Solutions Chapter 8.2 Ionic and Covalent Bonding

Detailed explanations in West Bengal Board Class 10 Physical Science Book Solutions Chapter 8.2 Ionic and Covalent Bondings offer valuable context and analysis.

WBBSE Class 10 Physical Science Chapter 8.2 Question Answer – Ionic and Covalent Bonding

Very Short Answer Type Questions :

Question 1.
What is a chemical bond?
Answer:
Chemical bond is a strong force of attraction that holds together atoms in a molecule or crystal.

Question 2.
What is the electronic configuration of noble gases in their valence shell ?
Answer:
Noble gases (except helium) have eight electrons in their valence shell i.e. they have ns², np⁶ configuration.

Question 3.
Why noble gases are inert?
Answer:
The inert nature of noble gases is due to their stable electronic configuration.

Question 4.
How does electrovalency occur?
Answer:
Electrovalency occurs due to shifting of electron.

Question 5.
What is the common reason behind the phenomena of electron release and electron sharing by elements?
Answer:
This is due to the tendency of elements to attain stable state of their nearest elements in periodic table.

Question 6.
What type of valency would be exhibited when an element combines with sodium ?
Answer:
Electrovalency.

Question 7.
Why are electrovalent compounds generally solid ?
Answer:
Electrovalent compounds are generally solid due to strong attractive electrostatic force between ions of opposite charges.

Question 8.
How is the valency of an element in an electrovalent compound measured ?
Answer:
The valency of an element in an electrovalent compound is measured by the number of electrons gained or lost by one atom of the element.

Question 9.
Name a covalent compound.
Answer:
Water (H₂O) is covalent compound.

Question 10.
Name an electrovalent compound.
Answer:
Sodium chloride (NaCl) is an electrovalent compound.

Question 11.
Name the type of valency where electrons are shared ?
Answer:
Electrons are shared in covalency.

Question 12.
Which class of substance is a common component of all electrovalent compounds ?
Answer:
A metal is common component of all electrovalent compounds.

Question 13.
State one characteristic of covalent compounds.
Answer:
Covalent compounds do not produce ions in solution or in fused states, so these are non-electrolytes.

Question 14.
What is the valency of carbon in CH₄ compound?
Answer:
The valency of carbon is 4 in CH₄ compound.

Question 15.
What is the nature of ionic bond ?
Answer:
Tonic bond is non-directional in nature.

Question 16.
SnCl₄ is a poor conductor of electricity. Why ?
Answer:
SnCl₄ being a covalent compound does not ionise and hence is a poor coductor of electricity.

Question 17.
What is the C – C bond length in saturated compounds ?
Answer:
The C-C bond length in saturated compounds is 1.54A°

Question 18.
What is the structure of ammonia ?
Answer:
The structure of ammonia is pyramidal.

Question 19.
What is the nature of bond formed between Cs and F ?
Answer:
The nature of bond formed between Cs and F is ionic.

Question 20.
Name of compound which contains both ionic and covalent bond.
Answer:
Potassium cyanide (KCN)

Question 21.
How many electrons take in forming bonds in N₂ ?
Answer:
The total number of electrons that take part in forming bonds in N₂ is 6.

Question 22.
Name the element which has highest electronegativity.
Answer:
‘F’ has highest electronegativity (4.0).

Question 23.
Consider two elements with atomic no. 37 and 53. What will be the bond between their atoms?
Answer:
Covalent.

Question 24.
What will be the shape of ethane?
Answer:
The shape of ethane is tetrahedral.

Question 25.
What is the type of bonding in ferric chloride ?
Answer:
The lype of bonding in ferric chloride is covalent.

Question 26.
Name an element which has zero electronegativity?
Answer:
Helium has zero electronegativity.

Question 27.
How many lone pair(s) is/are present XeOF₄ ?
Answer:
1 (one).

Question 28.
On which does lattice energy of an ionic compound depend ?
Answer:
Lattice energy of an ionic compound depends upon charge and size of the ion.

Question 29.
Give the name of one electrovalent substance which is used in everyday life.
Answer:
Sodium chloride (NaCl)

Question 30.
Give the name of one covalent substance which is used in everyday life.
Answer:
Water (H₂O).

Question 31.
Which one of NaCl and C₆ H₁₂ O₆ will have higher melting point?
Answer:
NaCl.

Question 32.
What types of bonds are expected between hydrogen atom and chlorine atom is HCI(g) molecule ?
Answer:
Covalent.

Question 33.
Atomic numbers of two elements A and B are 20 and 17 respectively. What would be the nature of the bond (covalent or electrovalent) between them if they combine chemically among themselves ?
Answer:
Electrovalent.

Question 34.
How many electrons are there in the outermost shell of the atom of the element carbon?
Answer:
four (4).

Question 35.
Between MgCl₂ and CHCl₃ which one is electrovalent in nature?
Answer:
MgCl₂.

Question 36.
What do you mean by valence shell ?
Answer:
The outermost shell of an atom is known as valence shell.

Question 37.
What is the nearest inert element of chlorine atom ?
Answer:
The nearest inert element of chlorine atom is argen (Ar).

Question 38.
What is the valency present in NaH ?
Answer:
Electrovalency is present in NaH.

Question 39.
What is the nearest inert element of carbon ?
Answer:
The nerest inert element of carbon is neon (Ne).

Question 40.
What are the types of Covalent bond ?
Answer:
Covalent bonds are of three types.
They are : (i) Covalent single bond (ii) covalent double bond (iii) coval at triple bond

Question 41.
What kind of bonding is present in substances which are nonelectrolytes?
Answer:
Covalent Bonding

Question 42.
The lonic crystals are always brittle-why?
Answer:
If mechanical pressure is applied to an ionic crystal then ions of similar charges may be forced to get closer to each other. By doing so, the electrostatic repulsion can be enough to split or disorient the lattice structure completely. This imparts brittleness to the structure.

Question 43.
Who proposed the electron dot structures to describe the bonding in simple covalent compounds ?
Answer:
Lewis proposed the electron dot structures to describe the bonding in simple covalent compounds.

Question 44.
Which bond has directional property?
Answer:
Covalent bonds have directional property.

Question 45.
Ionic bonds are non-directional in nature why?
Answer:
The attractive forces between ions in ionic compounds expend equally in all possible directions. It acts neither in a specific direction nor in confined to two particular ions. So, ionic bonds are non-directional in nature.

Question 46.
Give example of a covalent compound which can conduct electricity in aqueous solution.
Answer:
Hydrogen chloride ( HCl), though a covalent compound, undergoes complete ionization in water and conducts electricity in its aqueous solution.

Question 47.
Write the name of an ionic compound in which both the atoms of the component elements do not have octet.
Answer:
Lithium hydride (LiH) is the ionic compound in which both Li and H have duplet and not octet.

Question 48.
Sulphur is soluble in carbon disulphide but insoluble in waterexplain why?
Answer:
Carbon disulphide is a non-polar solvent and water is a polar solvent. Sulphur, being a covalent element molecule, is therefore soluble in non-polar carbon disulphide but not in water.

Short Answer Type Questions :

Question 1.
What are the causes of chemical combination ?
Answer:
Cause of chemical combination :
(i) Tendency to acquire noble gas configuration.
(ii) Tendency to acquire minimum energy.

Question 2.
What are the common types of bonds ?
Answer:
Depending upon the mode of acquiring nerest noble gas configuration, there are three common types of bonds :
(i) Ionic or Electrovalent bond, (ii) Covalent bond and (iii) Co-ordinate or Dative bond.

Question 3.
What are the main types of physical bonds ?
Answer:
The main types of physical bonds are : (i) Hydrogen bond, (ii) Metallic bond, (iii) Van der Waal’s interactions

Question 4.
What is the electronic theory of bonding ?
Answer:
Electronic theory of bonding : Atoms combine by transfer of electrons (ionic bonding) or by sharing of electrons (covalent bonding).

Question 5.
What is lonic bonding ?
Answer:
Ionic bonding : The electrostatic force of attraction which holds the oppositely charged ions together is called ionic bond or electrovalent bond and the compounds which are formed by the transference of electrons from one atom to other are known as ionic or electrovalent compounds. The number of electrons which an atom loses or gains while forming an ionic bond is known as electrovalency.

Question 6.
What are the conditions necessary for the formation of lonic bond ?
Answer:
Conditions necessary for the formation of Ionic bond :

1. Formation of cation from a neutral atom having low ionisation energy.
2. Formation of an anion from a neutral atom with high value of electron affinity.
3. Formation of crystal lattice from oppositely charged ions involving large release of energy.

Question 7.
What is Lattice energy ?
Answer:
Lattice energy : Lattice energy of an ionic solid is the amount of energy released when required number of cations and anions combine to form one mole of an ionic solid.

Question 8.
What are the factors by which Lattice energy depends ?
Answer:
Lattice energy depends upon the following factors :

1. Magnitude of charge of ions : It increases with increase in charge on cation, anion or both.
2. Size of cation : For a common anion, the lattice energy decreases with increase in size.
3. Size of anion : For a common cation, the lattice energy decreases, with increase size of anion.

Question 9.
What are the characteristics of ionic compounds ?
Answer:
Characteristics of ionic compounds :

1. All ionic compounds are usually crystalline solids and are composed of ions even in the solid state.
2. Ionic solid have high melting points and boiling points due to the presence of strong attractive forces between the oppositely charged ions.
3. Ionic compounds have low volatility high density and high stabiliy.
4. lonic compounds are highly soluble in polar solvents (such as water) having high dielectric constant (80) but insoluble in organic solvents (such as benzene, alcohol. ether etc.)

Question 10.
What type of valency is shown when sodium combines chemically with chlorine?
Draw the relevant electron dot diagram.
Answer:
Electrovalency is shown when sodium combine chemically with chlorine.
Electron dot diagram :

Question 11.
State the common reason behind the phenomena of electron release or electron capture by atoms to form ions.
Answer:
Explanation : An element goes into chemical bondage with another element since it tends to attain the stable state of its nearest inert element in the periodic table. To fulfill this, an atom either gains or loses electrons to possess 8 electrons or 2 electrons (for hydrogen atoms) in its outermost orbit. As a result of losing electrons, atoms are transformed to positive ions and on gaining electrons atoms transform to negative ions.

Question 12.
What type of valency is shown in Li₂O ? Draw the relevant electron dot diagram.
Answer:
Li₂ O Shows electrovalency.
Electron dot diagram :

Question 13.
What type of bonding is present in CaO ?
Answer:
Ionic bonding is present in CaO
Electron dot diagram :

Question 14.
What type of bonding is present in MgCl₂ ?
Answer:
Ionic bonding is present in MgCl₂
Electron dot diagram :

Question 15.
What type of valency is shown in Al₂ O₃ ?
Answer:
Flectron dot diagram :

Question 16.
What is covalent bond?
Answer:
Covalent bond (G.N. Lewis, 1916): A covalent bond is formed by the mutual sharing of electrons between the atoms, both of which are short electrons. The compound so formed is called covalent compounds. The member of electrons contributed by an atom for sharing is known as its covalency. Depending upon the number of electrons shared between two atoms being one, two or three, we have single covalent bond (: or = ), double covalent bond (:: or = ) and triple covalent bond ( :: or ≡ ).

Question 17.
What is octet rule ?
Answer:
Octet rule It states that atoms react because they have a tendency to complete their octet (or duplet) i.e. to have eight electrons in the valence shell (or two electrons if only one shell is present). They can do so by losing, gaining or sharing electrons.

Question 18.
What are the exceptions of octet rule ?
Answer:
Exceptions of octet rule There are many atoms which do not obey the octet rule and may contain six (as in BF₃ ), ten (as in PF₃ ) electrons.

Question 19.
What are the characteristics of covalent compounds?
Answer:
Characteristics of covalent compounds :

1. Covalent compounds exist in solid, liquid and gaseous state.
2. These compounds have low melting and boiling points.
3. These (except graphite) are bad conductors and react slowly.
4. These are soluble in non-polar solvents such as benzene, acetone etc., but are insoluble in polar solvents such as water.
5. Due to the directional nature of covalent bonds, these compounds show stereoisomerism.

Question 20.
What type of bonding is present in nitrogen molecule ?
Answer:
Covalent bonds are present in nitrogen molecule :
Diagram :

Question 20.
What type of bonding is present in oxygen molecule ?
Answer:
Covalent bonds are present in oxygen molecule.
Diagram :

Question 21.
What type of bonding is present in hydrogen molecule ?
Answer:
Covalent bond is present in hydrogen molecule.
Diagram :

Question 22.
How HCl(g) molecule is formed ?
Answer:
Covalent bond is present in HCl(g) molecule.
Diagram :

Question 23.
How water molecule is formed ?
Answer:
There are two covalent bonds in water molecule.
Diagram :

Question 24.
How methane molecule is formed?
Answer:
These are four covalent bonds in methane molecule.
Diagram :

Question 25.
How ammonia molecule is formed ?
Answer:
These are three covalent bonds in ammonia molecule.
Diagram :

Question 26.
How carbon dioxide molecule is formed ?
Answer:
These are four covalent bonds present in carbon dioxide molecule.
Diagram :

Question 27.
Why does the tendency of sharing electrons grows in many nonmetallic atoms during formation of covalent compounds ?
Answer:
Explanation : During formation of covalent compounds of non-metallic atoms, each participant involved in the process tends to attain duplet or octet stable state. To attain such stable state they share electrons.

Question 28.
Writ town the electronic configuration of a chlorine atom, a chlorine ion.
Answer:
Electronic configuration of chlorine atom is : 2, 8, 7.
Electronic configuration of a chlorine ion is : 2, 8, 8.

Question 29.
What is co-ordinate bond or dative bond ?
Answer:
Co-ordinate bond : It is a special type of covalent bonding where the shared pair of electrons is supplied only by one of the atoms forming the bond. The atom which supplies the shared pair of electrons is called donar while the atom which only uses the shared pair of electrons is called acceptor. e.g. Ammonium ion (\(\mathrm{NH}_4⁺}\))

Question 30.
SnCl₄ is a poor conductor of electricity. Why ?
Answer:
Explanation SnCl₄ being a covalent compound does not ionise and hence, is a poor conductor of electricity.

Question 31.
Covalency possesses directional properties but electrovalency has no such characteristics. Why ?
Answer:
Explanation Shared electron pairs of covalent bonds are localised between two atoms. Hence covalent bonds have directional character on the other hand oppositely changed ions in electrovalent compounds are held together by electrostatic forces of attraction which in non-directional in nature.

Question 32.
HCI gas is a covalent compound but its water solution conducts electricity. Why ?
Answer:
Explanation Electro-negativity of Cl and H are 3 and 2.1 respectively. The difference in the electro-negativities of Cl and H being 0.9, the bond in HCl is a polar covalent bond. When gaseous HCl is dissolved in water, then due to high dielectric constant of water (80), it breaks apart, the positive and negative ends of the dipole in HCl molecule giving H₃ O⁺ and Cl^– ions which conduct electricity.
HCl(g) + H₂O(l) → H₃O⁺ (aq) + Cl^– (aq)

Question 33.
Amongst LiF and Lil which has more covalent character and why ?
Answer:
Explanation : Lil has more covalent character because Li⁺cation will be able to polarize the bigger I^–more than the smaller F^–ion. Greater polarisation in Lil leads to more covalent character.

Question 34.
Water is generally a good solvent for lonic compounds. Why ?
Answer:
Explanation : Dielectric constant of water being high (80), the electrostatic force of attraction between oppositely charged ions gets reduced to (1/80) of original force in air. Hence, ions of an electrovalent compound get separated which then solvated by waters.

Broad Answer Type Questions: 

Question 1.
What is the difference between ionic compounds and covalent compounds ?
Answer:
Difference between ionic and covalent compounds :

Ionic Compounds	Covalent Compounds
i. These are formed by the transfer of one or more electrons from one atom to another.	i. These are formed by the sharing of one or more electrons between the bonded atoms.
ii. These consist of ions.	ii. These consist of individual molecules.
iii. These are soluble in water but insoluble in organic solvents.	iii. These are insoluble in water but soluble in organic solvents.
iv. These are hard solids with high melting and boiling points.	iv. These exist as gases, liquids or soft solids with low melting and boiling points.
v. These undergo ionic reactions which are very fast.	v. These undergo molecular reactions which are very slow.
vi. These conduct electricity in fused as well as aqueous solutions.	vi. These do not conduct electricity.
vii. These do not show isomerism.	vii. These show isomerism.

Question 2.
The atomic number of the element A is 20 and that of another element B is 17. Write down their electronic configurations. Will they produce an electrovalent compound or a covalent compound ? What will be their valencies in that case?
Answer:
Electronic configuration of A is : 2,8,8,2.
Electronic configuration of B is : 2,8,7.
They will produce and electrovalent compound.
Explanation . An atom A will give up two (2) valence electrons, each of two atoms of B will capture one electron. In the process atoms of A and B attain stable octet state and atoms of A will be positive ions and those of B will be negative ions. A and B thus form electrovalent compound.
As, an atom of A loses two electrons. So A has valency 2 (two) and since each atom of B captures one electron, the valency of B will be one (1).

Question 3.
Write down electronic arrangement of the element \({ }_{17}^{35} \mathrm{X}\)
1. what is the valency of the element?
2. will the element form anion or cation?
3. what type of valency will be exhibited when the element combines with sodium?
Answer:
The electronic configuration of the element X is : 2,8,7,

1. As an atom of the element tends of capture or share one electron to attain stable of octet, its valency is 1.
2. It will form anion by capturing electron.
3. The element will exhibit electro-valency when it combines with sodium since sodium is a metal, and atom of which tends to release one electron.