Periodic Table — Set 3

Correct Answer: C. Formed between two non-metals

• **Non-metal bonding** = Covalent bonds typically form between non-metal atoms that share electrons to fill their octets. • **Common occurrence** — Most organic compounds and non-metallic substances form through covalent bonding. • 💡 Wrong-option analysis: A: Covalent compounds can be solids, liquids, or gases; B: Most are poor conductors unless ionized; D: Covalents contain no metallic elements.

Correct Answer: C. Bond length

• **Bond length definition** = Bond length is the average distance between the centers of two bonded atoms at equilibrium. • **Optimal distance** — This distance represents where attractive and repulsive forces balance perfectly. • 💡 Wrong-option analysis: A: Bond displacement is not a standard term; B: Ionic radius measures ion size; D: Atomic radius measures atom size.

Correct Answer: C. H₂O

• **Water geometry** = Water molecules have a bent shape due to two lone pairs on the oxygen atom. • **Lone pair repulsion** — These lone pairs repel more strongly than bonding pairs, pushing the two O-H bonds together. • 💡 Wrong-option analysis: A: BeCl₂ is linear; B: BF₃ is trigonal planar; D: CO₂ is linear.

Correct Answer: D. Ductility

• **Ductility property** = Ductility is a physical property of metals enabled by their unique metallic bonding. • **Wire formation** — The sea of electrons allows metal atoms to slide past each other without breaking bonds, allowing wire drawing. • 💡 Wrong-option analysis: A: Luster is shininess; B: Malleability is flattening into sheets; C: Brittleness means easily broken.

Correct Answer: D. Calcium Oxide

• **Calcium Oxide** = CaO is formed by the complete transfer of electrons from Calcium to Oxygen, creating an electrovalent (ionic) bond. • **Ion formation** — Calcium becomes Ca²⁺ and Oxygen becomes O²⁻ through this electron transfer. • 💡 Wrong-option analysis: A: Glucose is covalent; B: Water is covalent; C: Ammonia is covalent.

Correct Answer: A. 1

• **One lone pair** = Nitrogen has five valence electrons; three are used to bond with hydrogen atoms, leaving one lone pair. • **Trigonal pyramidal** — This lone pair is responsible for ammonia's pyramidal shape and its ability to accept protons. • 💡 Wrong-option analysis: B: Two pairs would require two more atoms; C: Zero would mean no electrons left after bonding; D: Three pairs is impossible with three bonded atoms.

Correct Answer: C. VSEPR Theory

• **VSEPR theory** = VSEPR stands for Valence Shell Electron Pair Repulsion theory, explaining molecular shapes. • **Pair repulsion** — Electron pairs (bonding and lone) repel each other to minimize repulsion, determining 3D geometry. • 💡 Wrong-option analysis: A: Atomic theory concerns atom structure; B: Molecular orbital theory uses quantum mechanics; D: Kinetic theory concerns gas behavior.

Correct Answer: D. Molten or dissolved in water

• **Mobile ions** = In molten or dissolved states, ions are free to move and carry electric current. • **Fixed solid state** — In solid form, ions are locked in the lattice and cannot move to conduct electricity. • 💡 Wrong-option analysis: A: Not in gaseous state; B: Solids don't conduct due to fixed positions; C: Ionic compounds do conduct when melted/dissolved.

Correct Answer: A. 2

• **Period 1 maximum** = Period 1 elements like Hydrogen and Helium only have the 1s orbital. • **Two electron capacity** — The s orbital can hold maximum two electrons, so Period 1 can hold only 2 valence electrons. • 💡 Wrong-option analysis: B: 32 is for Period 5; C: 18 is for Period 4; D: 8 is for Periods 2-3.

Correct Answer: B. Non-polar covalent

• **Identical atoms** = A chlorine molecule consists of two identical atoms sharing a pair of electrons equally. • **No polarity** — Since both atoms have the same electronegativity, the bond is non-polar. • 💡 Wrong-option analysis: A: Ionic involves electron transfer; C: Polar requires different atoms; D: Metallic applies to metals, not diatomic molecules.