Chemical Bonding — Set 1

Correct Answer: D. Ionic bond

• **Ionic bond** = An ionic bond is formed by the complete transfer of electrons from a metal atom to a non-metal atom. • **Electrostatic attraction** — The resulting oppositely charged ions attract each other strongly through electrostatic forces. • 💡 Wrong-option analysis: A: Hydrogen bond is an intermolecular force between hydrogen and electronegative atoms; B: Metallic bond exists between metal atoms with delocalized electrons; C: Covalent bond involves sharing of electrons between atoms.

Correct Answer: C. 109.5 degrees

• **109.5 degrees** = The bond angle in methane results from its tetrahedral geometry with sp3 hybridized carbon. • **Tetrahedral shape** — Four electron pairs around carbon repel equally, forcing atoms into a pyramid-like 3D arrangement. • 💡 Wrong-option analysis: A: 120 degrees occurs in trigonal planar geometry; B: 180 degrees is found in linear molecules; D: 90 degrees is not a standard hybridization angle.

Correct Answer: A. Nitrogen

• **N≡N triple bond** = Nitrogen molecule has one of the strongest bonds known, with three shared electron pairs between two atoms. • **Inert gas** — The triple bond makes N2 extremely stable and unreactive under normal conditions. • 💡 Wrong-option analysis: B: Hydrogen has only a single bond; C: Oxygen has a double bond, not triple; D: Methane contains only single C-H bonds.

Correct Answer: A. London dispersion force

• **London dispersion force** = These are the weakest intermolecular forces resulting from temporary dipoles created by electron movement. • **All molecules experience** — Both polar and non-polar molecules exhibit London forces, making them universal interactions. • 💡 Wrong-option analysis: B: Ionic force is between charged ions, not non-polar molecules; C: Covalent force is an intramolecular bond, not intermolecular; D: Dipole-dipole force requires permanent dipoles, not applicable to non-polar molecules.

Correct Answer: D. Linear

• **Linear geometry** = sp hybridized atoms have two electron pairs arranged as far apart as possible in space. • **180-degree angle** — The orbitals align in opposite directions creating a perfectly straight molecular shape. • 💡 Wrong-option analysis: A: Trigonal planar occurs with sp2 hybridization; B: Octahedral requires d orbital involvement; C: Tetrahedral is characteristic of sp3 hybridization.

Correct Answer: B. Diamond

• **Diamond structure** = Each carbon atom bonds to four others in a rigid 3D tetrahedral network with no weak points. • **Highest melting point** — Diamond melts above **3550°C**, requiring massive energy to break countless strong C-C covalent bonds throughout. • 💡 Wrong-option analysis: A: Ice is held by hydrogen bonds, not covalent; C: Dry ice is held by weak London forces; D: Sodium chloride is ionic, not covalent network.

Correct Answer: C. Hydrogen bond

• **Hydrogen bonding** = A hydrogen atom bonded to oxygen in one water molecule attracts the lone pair on oxygen in another molecule. • **Partial charges** — The electronegativity difference creates δ+ on H and δ- on O, enabling strong intermolecular attraction. • 💡 Wrong-option analysis: A: Ionic bonds transfer electrons completely; B: Coordinate bonds are intramolecular; D: Metallic bonding occurs between metal atoms, not water molecules.

Correct Answer: C. Covalent bond

• **Covalent bonding** = Both atoms equally attract the shared electron pair when their electronegativities are similar, creating a non-polar bond. • **Electron cloud** — The electrons spend equal time around both nuclei, producing stable molecular structures like H2 and Cl2. • 💡 Wrong-option analysis: A: Coordinate bonds have electrons from one atom; B: Metallic bonding involves electron sea, not sharing; D: Ionic bonding transfers electrons, not shares them.

Correct Answer: C. Water

• **Bent geometry** = Water has two lone pairs on oxygen that occupy more space than bonding pairs, compressing the H-O-H angle. • **104.5 degrees** — VSEPR theory predicts this angle when four electron pairs (two lone, two bonding) occupy tetrahedral positions. • 💡 Wrong-option analysis: A: Boron trifluoride has trigonal planar shape with no lone pairs; B: Ammonia is trigonal pyramidal; D: Carbon dioxide is linear with no lone pairs.

Correct Answer: A. One atom

• **One atom donates** = The donor atom provides both electrons to the bond while the acceptor atom provides the empty orbital. • **Dative bond** — Once formed, it behaves like a regular covalent bond with equal electron sharing. • 💡 Wrong-option analysis: B: Three atoms would create a three-center bond; C: Zero atoms cannot form any bond; D: Two atoms means both contribute, which is regular covalent bonding.