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Chapter 3· Chemical Bonding
MCQs with Answers Try each one first: tap an option to check it, then read the reasoning and why the others are wrong.
A note about the questions
The wording follows published solved exercises and every answer was re-checked by hand, so the wording or the order of options may differ slightly from your print.
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Set A: Textbook exercise 10 MCQs The multiple-choice questions at the end of Chapter 3 in your book, in the book's option order.
Q3.1 Metallic Bond
When molten copper and molten zinc are mixed together, they give rise to a new substance called brass. Predict what type of bond is formed between copper and zinc.
(a) Coordinate covalent bond (b) Ionic bond (c) Metallic bond (d) Covalent bond Show answer and reasoning Answer (c) Metallic bond
Step by step
Copper and zinc are both metals. Metal atoms bond by sharing a sea of delocalised electrons: a metallic bond. Why the others are wrong
(a) a coordinate bond needs a donor with a lone pair and an acceptor, as in NH₃→BF₃.(b) an ionic bond forms between a metal and a non-metal, by electron transfer.(d) covalent bonds form between non-metals by sharing pairs.Remember
Metal + metal (an alloy) = metallic bond.
Q3.2 Coordinate Covalent Bond
Which element is capable of forming all the three types of bonds; covalent, coordinate covalent and ionic?
(a) Carbon (b) Oxygen (c) Magnesium (d) Silicon Show answer and reasoning Answer (b) Oxygen
Step by step
Ionic: Mg²⁺O²⁻. Covalent: H–O–H. Coordinate: H₂O: → H⁺ gives H₃O⁺. Why the others are wrong
(a) carbon normally only shares electrons (covalent); it does not readily form simple ions.(c) magnesium is a metal: ionic and metallic bonds only.(d) silicon forms covalent bonds (SiO₂, SiH₄).Remember
Needs to gain electrons, share them and own a lone pair: oxygen.
Q3.3 Intermolecular Forces
Why is H₂O a liquid while H₂S is a gas?
(a) Because in water, the atomic size of oxygen is smaller than that of sulphur (b) Because water is a polar compound and there exist strong forces of attraction between its molecules (c) Because H₂O molecule is lighter than H₂S (d) Because water can easily freeze into ice Show answer and reasoning Answer (b) Because water is a polar compound and there exist strong forces of attraction between its molecules
Step by step
Strong intermolecular forces: higher boiling point. Water has hydrogen bonding; H₂S does not. Why the others are wrong
(a) a smaller atom alone does not make a liquid; it is the strong attraction between water molecules that does.(c) being lighter would make water more of a gas, not less.(d) freezing has nothing to do with being a liquid at room temperature.Remember
Liquid vs gas = strength of forces between molecules.
Q3.4 Covalent Bond
Which of the following bonds is expected to be the weakest?
(a) C–C (b) Cl–Cl (c) O–O (d) F–F Show answer and reasoning Answer (c) O–O
Step by step
Small atoms with lone pairs (O, F) repel each other's lone pairs, weakening the bond. O–O 146 kJ/mol < F–F 158 kJ/mol. Why the others are wrong
(a) C–C (348 kJ/mol) is the strongest of the four.(b) Cl–Cl is 242 kJ/mol.(d) F–F (158 kJ/mol) is weak, but slightly stronger than O–O. Some solved copies key F–F.Remember
O–O and F–F are both weak; O–O is weaker (that is why peroxides like H₂O₂ break up easily).
Q3.5 Bonding and Properties
Which form of carbon is used as a lubricant?
(a) Coal (b) Diamond (c) Graphite (d) Charcoal Show answer and reasoning Answer (c) Graphite
Step by step
Layers held by weak forces. They slip past each other: slippery, a lubricant. Why the others are wrong
(a) coal is amorphous carbon, used as a fuel.(b) diamond is the hardest substance, used for cutting and drilling.(d) charcoal is amorphous carbon, used as a fuel and absorbent.Remember
Slippery layers: graphite.
Q3.6 Intermolecular Forces
Keeping in view the intermolecular forces of attraction, indicate which compound has the highest boiling point.
Show answer and reasoning Answer (a) H₂O
Step by step
H₂O, HF and NH₃ all hydrogen-bond; H₂S does not. Water forms the most hydrogen bonds per molecule: highest boiling point. Why the others are wrong
(b) H₂S has no hydrogen bonding; it boils at −60 °C.(c) HF hydrogen-bonds strongly but forms fewer bonds per molecule; it boils at 19.5 °C.(d) N is less electronegative than O; NH₃ boils at −33 °C.Remember
Water boils at 100 °C; the others are gases or near-gases at room temperature.
Q3.7 Metallic Bond
Which metal has the lowest melting point?
Show answer and reasoning Answer (d) Rb
Step by step
All give one electron to the electron sea. Bigger ion: weaker attraction to the sea: lower melting point. Rb is the biggest of the four. Why the others are wrong
(a) lithium has the highest melting point of the four, 181 °C.(b) sodium melts at 98 °C.(c) potassium melts at 63 °C.Remember
Alkali metals: melting point falls down the group.
Q3.8 Ionic Bond
Which ionic compound has the highest melting point?
(a) NaCl (b) KCl (c) LiCl (d) RbCl Show answer and reasoning Answer (a) NaCl
Step by step
Smaller cation: stronger attraction (NaCl > KCl > RbCl). LiCl is the exception: partly covalent, 605 °C. Why the others are wrong
(b) KCl melts at 770 °C; K⁺ is bigger than Na⁺.(c) LiCl melts at only 605 °C because of its covalent character.(d) RbCl melts at 718 °C.Remember
Data beats the rule: NaCl melts at 801 °C.
Q3.9 Coordinate Covalent Bond
Which compound contains both covalent and ionic bonds?
(a) MgCl₂ (b) NH₄Cl (c) CaO (d) PCl₃ Show answer and reasoning Answer (b) NH₄Cl
Step by step
NH₃ + H⁺ → NH₄⁺: covalent and coordinate bonds. NH₄⁺ Cl⁻: ionic bond between the ions. Why the others are wrong
(a) MgCl₂ is purely ionic: Mg²⁺ and 2Cl⁻.(c) CaO is purely ionic: Ca²⁺ and O²⁻.(d) PCl₃ is purely covalent.Remember
A polyatomic ion in a salt (NH₄⁺, SO₄²⁻, NO₃⁻) means both kinds of bond.
Q3.10 Covalent Bond
Which among the following has a double covalent bond?
(a) Ethane (b) Methane (c) Ethylene (d) Acetylene Show answer and reasoning Answer (c) Ethylene
Step by step
-ane: single bonds; -ene: a double bond; -yne: a triple bond. Why the others are wrong
(a) ethane, C₂H₆, has only single bonds.(b) methane, CH₄, has four single bonds.(d) acetylene, HC≡CH, has a triple bond.Set B: More MCQs from this chapter 14 MCQs Extra questions on the same ideas, of the kind set in board papers and class tests.
QB1 Why Atoms Form Bonds
Which noble gas has only two electrons in its outermost shell?
(a) Neon (b) Helium (c) Argon (d) Krypton Show answer and reasoning Answer (b) Helium
Step by step
He: 2 (duplet). Ne, Ar, Kr, Xe: 8 (octet). Why the others are wrong
(a) neon is 2, 8: eight outer electrons.(c) argon is 2, 8, 8.(d) krypton has eight outer electrons.Remember
Duplet for H and He; octet for the rest.
QB2 Why Atoms Form Bonds
A sodium atom (2, 8, 1) gets a stable electronic configuration most easily by:
(a) gaining seven electrons (b) losing one electron (c) sharing one electron (d) losing two electrons Show answer and reasoning Answer (b) losing one electron
Step by step
Na: 2, 8, 1. Na → Na⁺ + e⁻: 2, 8 (like Ne). Why the others are wrong
(a) gaining seven electrons is far harder than losing one.(c) sodium reacts by transferring its electron, forming ions.(d) it has only one outer electron.Remember
Take the energetically easier path.
QB3 Ionic Bond
An ionic bond is the strong electrostatic attraction between:
(a) a shared pair of electrons and two nuclei (b) oppositely charged ions (c) positive ions and a sea of electrons (d) neighbouring polar molecules Show answer and reasoning Answer (b) oppositely charged ions
Step by step
Transfer of electrons makes cations and anions. Their attraction is the ionic bond. Why the others are wrong
(a) that is a covalent bond.(c) that is a metallic bond.(d) that is a dipole-dipole force between molecules.QB4 Covalent Bond
How many electrons are shared in a triple covalent bond?
Show answer and reasoning Answer (c) 6
Step by step
Each bond line is one shared pair (2 electrons). Three lines: 6 electrons. Why the others are wrong
(a) 3 is the number of pairs, not electrons.(b) 4 electrons make a double bond.(d) 2 electrons make a single bond.Remember
Electrons = 2 × number of lines.
QB5 Covalent Bond
Which molecule has a non-polar covalent bond?
Show answer and reasoning Answer (c) Cl₂
Step by step
Identical atoms: equal pull: non-polar. Different atoms: unequal pull: polar. Why the others are wrong
(a) Cl pulls the pair more than H: polar.(b) O–H bonds are polar.(d) N–H bonds are polar.Remember
Same atoms on both ends = non-polar.
QB6 Why Atoms Form Bonds
The most electronegative element in the periodic table is:
(a) oxygen (b) chlorine (c) nitrogen (d) fluorine Show answer and reasoning Answer (d) fluorine
Step by step
Electronegativity rises across a period and up a group. Fluorine is at the top right (noble gases aside). Why the others are wrong
(a) oxygen is second, 3.44.(b) chlorine is 3.16.(c) nitrogen is 3.04.Remember
F is the most electronegative.
QB7 Coordinate Covalent Bond
In the hydroxonium ion, H₃O⁺, the electron pair of the coordinate bond is donated by:
(a) the H⁺ ion (b) the oxygen atom of water (c) a hydrogen atom of water (d) the chloride ion Show answer and reasoning Answer (b) the oxygen atom of water
Step by step
H₂O has two lone pairs on O. H⁺ has an empty shell. O donates: H₂O → H⁺. Why the others are wrong
(a) H⁺ has no electrons; it is the acceptor.(c) the H atoms of water have no lone pairs.(d) no chloride is involved in forming H₃O⁺.Remember
The donor owns the lone pair.
QB8 Coordinate Covalent Bond
In the reaction NH₃ + BF₃ → H₃N→BF₃, the acceptor of the electron pair is:
(a) nitrogen (b) hydrogen (c) boron (d) fluorine Show answer and reasoning Answer (c) boron
Step by step
N in NH₃: one lone pair (donor). B in BF₃: 6 electrons, room for a pair (acceptor). Why the others are wrong
(a) nitrogen is the donor.(b) the hydrogen atoms already have their duplet.(d) fluorine already has an octet.Remember
The arrow points from the donor (N) to the acceptor (B).
QB9 Metallic Bond
Magnesium melts at a higher temperature (650 °C) than sodium (98 °C) because:
(a) magnesium atoms are lighter (b) each magnesium atom gives two electrons to the electron sea and forms Mg²⁺ (c) magnesium is a non-metal (d) magnesium has fewer electrons than sodium Show answer and reasoning Answer (b) each magnesium atom gives two electrons to the electron sea and forms Mg²⁺
Step by step
Na: Na⁺ + 1 e⁻ per atom. Mg: Mg²⁺ + 2 e⁻ per atom. More charge, more electrons: stronger bond, higher melting point. Why the others are wrong
(a) magnesium atoms (24) are heavier than sodium atoms (23), and mass is not the reason.(c) magnesium is a metal.(d) magnesium has more electrons (12) than sodium (11).Remember
More electrons in the sea = stronger metallic bond.
QB10 Metallic Bond
Metals are good conductors of electricity because they have:
(a) free ions (b) mobile (delocalised) electrons (c) shared electron pairs (d) hydrogen bonds Show answer and reasoning Answer (b) mobile (delocalised) electrons
Step by step
Metallic bond: ions in a sea of electrons. Moving electrons carry charge. Why the others are wrong
(a) the metal ions stay in place; ions carry current in molten or dissolved ionic compounds.(c) shared pairs are fixed between two atoms in covalent bonds.(d) hydrogen bonds act between molecules like water.Remember
Metals: moving electrons. Molten salts: moving ions.
QB11 Intermolecular Forces
Hydrogen bonding occurs between molecules in which hydrogen is bonded to:
(a) C, Si or S (b) F, O or N (c) Na or K (d) Cl, Br or I Show answer and reasoning Answer (b) F, O or N
Step by step
Highly polar H–F, H–O, H–N bonds. Strong attraction between molecules: hydrogen bonds. Why the others are wrong
(a) C, Si and S are not electronegative enough.(c) Na and K are metals; NaH and KH are ionic.(d) Cl, Br and I are too large; HCl shows only dipole-dipole forces.Remember
FON: fluorine, oxygen, nitrogen.
QB12 Bonding and Properties
Solid sodium chloride does not conduct electricity because:
(a) it contains no ions (b) its ions are held in fixed positions and cannot move (c) it is a covalent compound (d) its electrons are shared Show answer and reasoning Answer (b) its ions are held in fixed positions and cannot move
Step by step
Current needs moving charged particles. Solid: ions fixed. Molten or aqueous: ions free. Why the others are wrong
(a) it is made of Na⁺ and Cl⁻ ions.(c) NaCl is ionic.(d) electrons are transferred in NaCl, not shared.Remember
Ionic: conducts only when molten or dissolved.
QB13 Bonding and Properties
When solutions of sodium chloride and silver nitrate are mixed, a white precipitate forms. The precipitate is:
(a) sodium nitrate (b) silver chloride (c) sodium metal (d) silver nitrate Show answer and reasoning Answer (b) silver chloride
Step by step
NaCl(aq) + AgNO₃(aq) → AgCl(s) + NaNO₃(aq). AgCl is insoluble: white precipitate. Why the others are wrong
(a) sodium nitrate is soluble and stays dissolved.(c) no sodium metal forms in water.(d) silver nitrate is a reactant and is soluble.Remember
Silver halides precipitate: AgCl white, AgBr cream, AgI yellow.
QB14 Bonding and Properties
Graphite conducts electricity but diamond does not because:
(a) graphite has mobile electrons between its layers (b) diamond contains ions (c) graphite is a metal (d) the bonds in diamond are weak Show answer and reasoning Answer (a) graphite has mobile electrons between its layers
Step by step
Graphite: 3 bonds per C, 1 mobile electron. Diamond: 4 bonds per C, no mobile electrons. Why the others are wrong
(b) diamond is a covalent network; it has no ions.(c) graphite is a form of carbon, a non-metal.(d) diamond's bonds are very strong; that is why it is so hard.Remember
Free electron = conductor.
