Selina ICSE Class 10 Chemistry Solutions Chapter 2 Chemical Bonding

Intext – Question- 1

Question 1: How do atoms attain noble gas configuration?
Solution 1:
Atoms attain noble gas configuration when their outer most shell is completely filled with the required number of electrons. To achieve a noble gas configuration, atoms usually lose, gain, or share electrons.

Question 2: Define:
(a) a chemical bond
(b) an electrovalent bond
(c) a covalent bond
Solution 2:
(a) A chemical bond can be described as the attraction between any two atoms in a molecule that keeps the molecule stable. Chemical bonds are formed due to the attraction of atoms.
(b) A chemical connection produced between two atoms by the transfer of one or more electrons from a metallic electropositive atom to a non-metallic electronegative atom.
(c) The chemical connection generated by the mutual sharing of electrons between non-metallic element atom pairs.

Question 3: What are the conditions for the formation of an electrovalent bond?
Solution 3:
(i) In order to form an ionic connection, the atom that becomes a cation must contain one, two, or three valency electrons. The other atom that forms an anion should have 5, 6, or 7 electrons in its valence shell.
(ii) A considerable difference in electronegativity between the two atoms is required to form an ionic connection.
(iii) Either a net loss of energy or energy liberation is required. The ionisation potential of one atom should be low, while the electron affinity of the other atom should be high.
(iv) An ionic compound is more likely to form if the lattice energy is high.

Question 4: An atom X has three electrons more than the noble gas configuration. What type of ion will it form? Write the formula of its
(i) sulphate
(ii) nitrate
(iii) phosphate
(iv) carbonate
(v) hydroxide
Solution 4:
It will form a cation:
M³⁺M₂(SO₄)₃
M(NO₃)₃
M₃(PO₄)₃
M₂(CO₃)₃
M(OH)₃

Question 5: Mention the basic tendency of an atom which makes it to combine with other atoms.
Solution 5:
By merging with other atoms, atoms create stable octet or noble gas configurations.

Question 6: What type of compounds are usually formed between metals and non-metals and why?
Solution 6:
Metals lose electrons to create cations all the time, but non-metals receive electrons to make anions to complete their octet, resulting in ionic compounds between metals and non-metals. These oppositely charged ions are held together by electrostatic attraction, forming an ionic compound.

Question 7: In the formation of the compound XY₂, an atom X gives one electron to each Y atom. What is the nature of bond in XY₂? Draw the electron dot structure of this compound.
Solution 7:
In the formation of the compound XY₂, an atom X gives one electron to each Y atom. In XY₂, X and Y are establishing an ionic connection

Question 8: An atom X has 2, 8, 7 electrons in its shell. It combines with Y having 1 electron in its outermost shell.
(a) What type of bond will be formed between X and Y?
(b) Write the formula of the compound formed.
Solution 8:
(a) Ionic connection will be formed between X and Y because X has seven electrons in its outermost shell whereas Y only has one electron. Y will lose that 1 electron and X will gain the electron lost by Y.
(b) The formula for the chemical would be XY.

Question 9: Draw orbit structure and electron dot diagram of NaCI, MgCl₂ and CaO.
Solution 9:
Orbit structure and electron dot diagram of NaCl:

Orbit structure and electron dot diagram of MgCl₂:

Orbit structure and electron dot diagram of CaO:

Question 10: Compare:
(a) sodium atom and sodium ion
(b) chlorine atom and chloride ion, with respect to
(i) atomic structure
(ii) electrical state
(iii) chemical action
(iv) toxicity
Solution 10:
(a) Comparison of the atom of sodium and the ion of sodium:
(i) The M shell of a sodium atom has one electron, but there are eight electrons in the L shell of a sodium ion.
(ii) The sodium atom is positively charged, whereas the sodium ion is neutral.
(iii) While the sodium atom is very reactive, the ion of sodium is inert.
(iv) The sodium atom is poisonous, but the sodium ion is not.
(b) Comparison of the atom of chlorine and the ion of chlorine:
(i) The M shell of the chlorine atom has seven electrons, while the M shell of the chloride ion has eight electrons.
(ii) The chloride ion is negatively charged, while the chlorine atom is neutral.
(iii) While the chlorine atom is very reactive, the ion of chlorine is inert.
(iv) Chlorine atom is harmful, although the chloride ion is not.

Question 11: The electronic configuration of fluoride ion is the same as that of a neon atom. What is the difference between the two?
Solution 11:
The electronic configuration of fluoride ion is the same as that of a neon atom. Fluoride ion is negatively charged while neon atom is neutral.

Intext – Question- 2

Question 1: What are the conditions necessary for the formation of covalent molecules?
Solution 1:
(i) The outermost shells of both atoms, i.e. non-metals, should have four or more electrons.
(ii) Both atoms’ electronegativity should be high.
(iii) Both atoms should have a strong electron affinity and ionisation potential.
(iv) The electronegativity difference between the two atoms should be zero or very small.
(v) The atoms’ vicinity to one another should culminate in an energy reduction.

Question 2: Elements A, B and C have atomic number 17, 19 and 10 respectively.
(a) State which one is: (i) a non-metal (ii) a metal, (iii) chemically inert?
(b) write down the formula of the compound formed by two of the above elements.
Solution 2:
(a) A with atomic number 17 is a non-metallic element.
Element B with atomic number 19 is a metal.
Element C is a chemically inert element.
(b) BA is the formula of the compound formed by two of the above elements.

Question 3: Five atoms are labeled from A to E

(a) Which one of these atoms:
(i) contains 7 protons,
(ii) has an electronic configuration 2, 7?
(b) Write down the formula of the compound formed between C and D.
(c) predict which are: (i) metals, (ii) non-metals?
Solution 3:
(a)
(i) Element E contains 7 protons.
(ii) Element B has an electronic configuration 2, 7.
(b) C₂D
(c) A and C are metals while B, D and E are non -metals.

Question 4: What is the difference between:
(a) ionic compounds and polar covalent compounds,
(b) ionic compounds and covalent compounds,
(c) a polar covalent compound and a non-polar covalent compound?
Solution 4:
(a) Ionic compound formed of ions held together with electrostatic forces termed as ionic bonds. These compounds are created when one or more electrons from a metallic electropositive element are transferred to a non-metallic electronegative element atom.
A polar covalent compound is one in which the electron distribution between the two atoms is uneven.
(b) Ionic compounds are crystalline solids with high melting and boiling temperatures composed up of ions which are held together with electrostatic forces termed as ionic bonds.
They are water soluble and strong electrical conductors in aqueous solution and molten state.
While Molecule-based covalent compounds occur as soft solids, liquids, or gases with low melting and boiling points.
They are often water insoluble and poor electrical conductors.
(c) Polar covalent compounds are generated when two non-metal atoms with distinct electro negativities share the same bound electron pair unequally. When two identical non-metals share electrons equally, non-polar compounds are created.

Question 5: The element X has the electronic configuration 2, 8, 18, 8, 1. Without identifying x,
(a) predict the sigh and charge on a simple ion of X.
(b) write if X be an oxidizing agent or reducing agent and why.
Solution 5:
(a) X+
(b) X will be a strong reducing agent as it will have the tendency to donate its valence electron.

Question 6: What do you understand by polar covalent compounds? Explain it by taking hydrogen chloride as an example.
Solution 6:
Polar covalent compounds are generated when two non-metal atoms with distinct electro negativities share the same bound electron pair unequally. When a common pair of electrons is unequally distributed between two atoms, a covalent compound is said to be polar. The high electronegativity of the chlorine atom, for example, draws the shared electron pair towards itself in HCl. As a result, it acquires a minor negative charge, whereas the hydrogen atom acquires a minor positive charge. As a result, a polar covalent bond forms.

Question 7: Methane molecule is non-polar molecule. Explain.
Solution 7:
The atoms involved in the formation of a non-polar covalent connection between two similar or dissimilar atoms share the electrons equally. Methane has four solitary carbon-hydrogen covalent connections in its molecule. Because the electrons are equally shared by the carbon and hydrogen atoms, it is a non-polar covalent molecule. As a result, the shared pair resides between the atoms at an equal distance from both carbon and hydrogen atoms.

Question 8: Give the characteristic properties of:
(a) Electrovalent compounds,
(b) covalent compounds.
Solution 8:
(a) Characteristic properties of Ionic Compound:
1. Ionic substances are frequently found as crystalline solids.
2. Melting and boiling points of ionic compounds are extremely high because they need a large amount of energy to break strong ionic bonds.
3. Ionic substances are insoluble in organic solvents but soluble in water.
4. In the fused or aqueous solution form, they are strong conductors of electricity.
(b) Characteristic properties of Covalent Compound:
1. Covalent compounds can be found in the form of gases, liquids, or soft solids.
2. Covalent compounds have low melting and boiling points in general.
3. Covalent substances are soluble in organic solvents but not in water.
4. In the solid, molten, or watery form, they are non-conductors of electricity.

Question 9: (a) What do you understand redox reactions? Explain oxidation and reduction in terms of loss or gain of electrons.
(b) Divide the following redox reactions into oxidation and reduction half reactions.
(i) Zn + Pb₂ → Zn₂ + Pb
(ii) Zn + Cu₂ → Zn₂ + Cu
(iii) CI₂ + 2Br → Br₂ + 2CI-
(iv) Sn₂ + 2Hg₂ → Sn₄ + Hg²⁺
(v) 2Cu + → Cu + Cu²⁺
(c) Potassium (at No .19) and chlorine (at No. 17) react to form a compound. Explain on the basis of electronic concept.
(i) oxidation
(ii) reduction
(iii) oxidizing agent
(iv) reducing agent
Solution 9:
(a) An oxidation-reduction reaction, or simply a redox reaction, occurs when oxidation and reduction occur at the same time.
The transfer of electrons between two chemical species is referred to as a redox reaction.
A reduction reaction is one in which an electron is gained, while an oxidation reaction is one in which an electron is lost.
The term “oxidised” refers to a chemical that has lost an electron, whereas “reduced” refers to a compound that has gained an electron.
(b)
(i) Oxidation :Zn → Zn 2+
Reduction : Pb2+ Pb
(ii) Oxidation : Zn → Zn 2+
Reduction : Cu2+ Cu
(iii) Oxidation : Br- → Br Reduction : Cl2 → 2Cl-
(iv) Oxidation : Sn2+ → Sn4+
Reduction : 2Hg2+ → Hg2
(v) Oxidation : Cu+ → Cu 2+
Reduction : Cu+ → Cu
(c)
(i)When potassium loses an electron, it oxidises and becomes a cation.
(ii) As chlorine obtains an electron, it undergoes reduction and creates the chloride anion.
(iii) Potassium is oxidised as a reducing agent.
(iv) Chlorine is an oxidising agent that causes it to be reduced.

Question 10: What do you understand by a dipole molecule? Give one example.
Solution 10:
A dipole molecule possesses a slight positive as well as a slight negative charge.
Hydrogen has a small positive charge in HCl, while chlorine has a slight negative charge. The dipole moment of the HCl molecule is 1.03 D, which is written as:

Intext – Question- 3

Question 1: Explain the following:
(a) Electrovalent compounds conduct electricity.
(b) Electrovalent compounds have a high melting point and boiling point while covalent compounds have low melting and boiling points.
(c) Electrovalent compounds dissolve in water whereas covalent compounds do not.
(d) Electrovalent compounds are usually hard crystals yet brittle.
(e) polar covalent compounds electricity.
Solution 1:
(a) Because ions cannot travel in the solid state due to their stiff structure, electrovalent substances in the solid state cannot conduct electricity. However, when these compounds are molten, they conduct electricity. This is conceivable because the electrostatic forces of attraction between oppositely charged ions are weak in the molten state. As a result, the ions are free to travel about and conduct electricity.
(b) In stable molecules, the atoms of covalent compounds are closely bonded to each other, but the molecules are not particularly strongly attracted to other molecules in the complex. The atoms (ions) in electrovalent compounds, on the other hand, have a significant attraction to other ions in their vicinity. For covalent solids, this results in low melting temperatures, while for electrovalent solids, it results in high melting points.
(c) Because the forces of attraction between positive and negative charges weaken in polar solvents like water, electrovalent substances dissolve. Covalent compounds, on the other hand, are composed up of molecules and so do not ionise or dissolve in water.
(d) Ionic compounds are extremely hard because it requires a lot of energy to separate the positive and negative charges. However, when stress is applied, ions with the same charge are drawn together, causing opposite ions to reject one another and the crystal to shatter.
(e) Polar covalent compounds conduct electricity in aqueous solution because they are made up of charged particles.

Question 2: A solid is crystalline, has a high melting point and is water soluble. Describe the nature of the solid.
Solution 2:
A solid is crystalline, has a high melting point and is water soluble because the oppositely charged ions are bound closely together by strong intermolecular forces of attraction; the solid is ionic in nature, which explains its high melting point and water solubility.

Question 3: Match the atomic number 4, 8, 14, 15 and 19 with each of the following:
(a) A solid non-metal of valelncy 3.
(b) A gas of valency 2.
(c) A metal of valency 1.
(d) A non-metal of valency 4.
Solution 3:
(a) A solid non-metal of valelncy 3 has atomic number 15.
(b) A gas of valency 2 has atomic number 8.
(c) A metal of valency 1 has atomic number 19.
(d) A non-metal of valency 4 has atomic number 14.

Question 4: Elements X, Y, and Z have atomic numbers 6, 9 and 12 respectively. Which one:
(a) forms an anion,
(b) forms a cation,
(c) State type of bond between Y and Z and give its molecular formula.
Solution 4:
(a) Y
(b) Z
(c) X

Question 5: Taking MgCI₂ as an electrovalent compound, CCI₄ as a covalent compound, give four differences between electrovalent and covalent compounds.

Electrovalent Compounds	Covalent compounds
They are made up of ions; Mg2+ and Cl–	They are made up of molecules; 1 carbon and 4 chlorine atoms form a molecule of CCl4.
They are made up of ions; Mg2+ and Cl–	They are generally gases or liquids under ordinary conditions; CCl4 is a liquid.
They have high melting point and boiling point.	Their melting point and boiling point are low.

Solution 5:

They are easily soluble in water but insoluble in organic solvents, such as benzene, chloroform, etc.

They are insoluble in water but are usually soluble in organic solvents, such as benzene, chloroform, etc.

Question 6: Potassium chloride is an electrovalent compound, while hydrogen chloride is a covalent compound. But, both conduct electricity in their aqueous solutions. Explain.
Solution 6:
In water, potassium chloride conducts electricity because the forces of attraction between positive and negative charged ions weaken, allowing the ions to move around.
The HCl bond, on the other hand, is a polar covalent molecule, meaning that H has a partial positive charge and Cl has a partial negative charge. As a result, it ionises in water, forming ions and conducting electricity.

Question 7: Name two compounds that are covalent when taken pure but produce ions when dissolved in water.
(a) For each compound mentioned above give the formulae of ions formed in aqueous solution.
Solution 7:
(a) HCl and H₂O
(b) H⁺ and Cl- ions And
H⁺ and O^2- ions

Question 8: An element M burns in oxygen to form an ionic bond MO. Write the formula of the compounds formed if this element is made to combine with chlorine and sulphur separately.
Solution 8:
Because M forms MO when it reacts with oxygen, it has a valency of +2. As a result, the formulas for chlorine and sulphur compounds are MCl₂ and MS, respectively.

Question 9: Give electron dot diagram of the following:
(a) Magnesium chloride
(b) nitrogen
(c) methane
Solution 9:

Question 10: State the type of bonding in the following molecules.
(a) Water
(b) Calcium oxide
(c) hydroxylion,
(d) methane,
(e) ammoniumion
(f) ammonium chloride
Solution 10:
(a) Water is a covalent bond.
(b) Calcium oxide is ionic bond.
(c) Hydroxyl ion is Polar covalent bond.
(d) Methane is covalent bond.
(e) Ammonium ion is Co-ordinate covalent bond.
(f) Ammonium chloride is covalent, coordinate and ionic bonds.

Question 11: Define a coordinate bond and give the conditions for its formation. Explain with an example.
Solution 11:
A coordinate bond is a bond established between two atoms by sharing a pair of electrons that are furnished totally by one of the combining atoms but shared by both. It’s illustrated by an arrow that starts with the donor atoms and ends with the acceptor.
1. At least one lone pair of electrons must exist in one of the two atoms.
2. At least one lone pair of electrons should be missing from another atom.
The two single electrons in the oxygen atom of water are used to create a coordination bond with the hydrogen ion, which is electron-deficient, resulting in the production of the hydronium ion.
H₂O + H+ H₃O H A coordinate covalent bond is formed when the hydrogen ion absorbs one lone pair of electrons from the oxygen atom of the water molecule.

Question 12: What do you understand by lone pair and shared pair?
(a) (i) How many atoms of each kind are present in the following molecules: calcium oxide, chlorine, water, carbon tetrachloride?
(ii) How many electrons are required for their octet structure?
Solution 12:
(a) A lone pair of electrons is a pair of electrons that are not shared by any other atom. Shared pair of electrons refers to the valence shell electrons that are shared by two atoms to create a covalent connection.
Calcium oxide is made composed of calcium and oxygen. To complete the octet structure, calcium must lose two electrons and oxygen must acquire two electrons. ii) A water molecule is made up of two hydrogen atoms and one oxygen atom. To complete its duplet, hydrogen atoms require one electron, while oxygen requires two electrons to complete its octet structure.
(b) There is one carbon atom and four chlorine atoms in carbon tetrachloride. Each of the four chlorine atoms needs one electron to complete its octet, whereas carbon requires four electrons to complete its octet.

Question 13: Complete the following:
(a) When the nuclei of two different reacting atoms are of mass, then a bond so
formed is called covalent bond (Equal, unequal, polar, non-polar).
(b) In case of non-polar covalent bond, the covalent bond is formed in the of atoms
and shared electrons are Distributed (corner, middle, equally, unequally).
(c) The ions in ……………… compounds are held very strongly due strong Forces
(electrovalent, covalent, electromagnetic, electrostatic).
Solution 13:
(a) When the nuclei of two different reacting atoms are of unequal mass, then a bond so formed is called polar covalent bond.
(b) Middle, equally In case of non-polar covalent bond, the covalent bond is formed in the middle of atoms and shared electrons are equally distributed.
(c) The ions in electrovalent compounds are held very strongly due strong electrostatic forces.

Question 14: (a) Draw an electron dot diagram to show the structure of each of the following:
(i) Hydronium ion,
(ii) Ammonium ion,
(iii) Hydroxylion.
State the type of bonding present in them.
(b) Give two example in each case:
(i) Co-ordinate bonds compounds,
(ii) solid covalent compounds,
(iii) Gaseous polar compounds,
(iv) Gaseous non polar compounds,
(v) Liquid non polar compounds.
Solution 14:
(a)

(i) Ammonium ion and hydronium ion
(ii) Phosphoruspenta chloride and diamond
(iii) Hydrogen chloride and water vapour
(iv) Oxygen gas and nitrogen gas
(v) Toluene and Gasoline

Question 15: Element M forms a chloride with the formula MCI₂ which is a solid with high melting point. M would most likely be in the group in which is placed.
[ (a)Na (b) Mg (c) Al (d) Si ]
Solution 15:
Element M forms a chloride with the formula MCI2 which is a solid with high melting point. M would most likely be in the group in which Mg is placed.

Question 16: Complete the following:
Solution 16:

	Sodium	Phosphorus	Carbon
Formula of chloride	NaCl	PCl5	CCl4
Nature of bonding	Ionic	Covalent	Covalent
Physical state of chloride	Solid	Solid	Liquid

Question : (a) Element X is a metal with a valency 2. Element Y is a non-metal with a valency3.
(i) Write equations to show how X and Y form ions.
(ii) If Y is a diatomic gas, write the equation for the direct combination of X and Y to form a compound.
(iii) If the compound formed between X and Y is melted and an electric current is passed through the molten compound, the element X will be obtained at the ……… and Y at the of the electrolytic cell.
Solution (2004):
(i) X – X²⁺ + 2e-
Y + 3e– Y^3-
(ii) 6X + 2Y₂ ¬¬- 2X₃Y₂
(iii) cathode , anode

Question : (a) Compound X consists of molecules.
Choose the letter corresponding to the correct answer from the options A, B, C and D given below:

(i) The type of bonding in X will be:
A. ionic
B. electrovalent
C. covalent
D. molecular

(ii) X is likely to have a:
A. low melting point and high boiling point,
B. high melting point and low boiling point
C. Low melting point and low boiling point,
D. high melting point and high boiling point.

(iii) In the liquid state, X will:
A. Become ionic
B. be an electrolyte
C. conduct electricity
D. not conduct electricity

(b) Electrons are getting added to an element Y:
(i) is Y getting oxidized or reduced?
(ii) what charge will Y migrate to during the process of electrolysis?

(c)
(i) Acidsdissolveinwaterandproducepositivelychargedions.Drawthestructureofthese positive ions.

(ii) Explain why carbon tetrachloride does not dissolve in water.

(iii) Elements Q and S react together to form an ionic compound. Under normal conditions, which physical state will the compound QS exist in?

(iv) Can Q and S, both be metals? Justify your answer.

Question : (a) Choose the correct answer from the choices A,B,C and D:

(i) The property which is characteristic of an electrovalent compound is that:
A. it is easily vaporized
B. it has a high melting point
C. it is a weak electrolyte,
D. it often exists as a liquid.

(ii) When a metal atom becomes anion:
A. It loses electrons and is Oxidized
B. It gains electrons and is reduced,
C. It gains electrons and is oxidized,
D. it loses electrons and is reduced.

(b) Identify the following reactions as either oxidation or reduction:
(i) O + 2e- → O^2-
(ii) K – e- →K+
(iii) Fe³ + e- →Fe²⁺

Question : (i) Name the charged particles which attract one another to form electrovalent compounds.
(ii) In the formation of electrovalent compounds, electrons are transferred from one element to another. How are electrons involved in the formation of a covalent compound?
(iii) The electronic configuration of nitrogen is (2, 5). How many electrons in the outer shell of a nitrogen atom are not involved in the formation of a nitrogen molecule?
(iv) In the formation of magnesium chloride (by direct combination between magnesium and chlorine), name the substance that is oxidized and the substance that is reduced.
Solution :
(i) Ions are charged particles which attract one another to form electrovalent compounds.
(ii) Electrons are shared between the atoms of two or more elements in the formation of covalent compound.
(iii) Two electrons in the outer shell of a nitrogen atom are not involved in the formation of a nitrogen molecule.
(iv) Magnesium is oxidized and chlorine is reduced in the formation of magnesium chloride (by direct combination between magnesium and chlorine).

Question : (a) Which of the following is not a common characteristic of an electrovalent compound?
A. High melting point
B. Conducts of electricity when molten.
C. Consists of oppositely charged ions
D. Ionizes when dissolved in water.
(b) What are the terms defined below?
(i) A bond formed by a shared pair of electrons, each bonding atom contributing one electron to the pair.
(ii) A bond formed by a shared pair of electrons with both electrons coming from the same atom.
Solution :
(a) D
(b)
(i) A bond formed by a shared pair of electrons, each bonding atom contributing one electron to the pair is covalent bond.
(ii) A bond formed by a shared pair of electrons with both electrons coming from the same atom is coordinate bond.