Periodic Table — Set 2
Chemistry · आवर्त सारणी · Questions 11–20 of 40
In a polar covalent bond, where are the shared electrons likely to be found?
Correct Answer: B. Closer to the more electronegative atom
• **Dipole formation** = Electrons in a polar bond are pulled toward the atom with higher electronegativity, creating a dipole. • **Charge distribution** — Results in a partially negative end near the more electronegative atom and partially positive end near the less electronegative atom. • 💡 Wrong-option analysis: A: Electrons move away from less electronegative atom; C: Unequal sharing defines polarity; D: Electrons don't orbit in figure-eights.
Which scientist is primarily associated with the Lewis Dot structures used to represent bonding?
Correct Answer: C. Gilbert N. Lewis
• **Gilbert N. Lewis** = Developed Lewis dot structures showing valence electrons as dots around element symbols. • **Visual representation** — This system helps visualize electron sharing and octet rule fulfillment in molecules. • 💡 Wrong-option analysis: A: Mendeleev created the periodic table; B: Pauling worked on electronegativity; D: Rutherford studied atomic structure.
What is the bond angle in a linear molecule like Carbon Dioxide (CO₂)?
Correct Answer: A. 180°
• **180 degree angle** = In carbon dioxide, the two double bonds stay as far apart as possible, resulting in a straight linear structure. • **Maximum separation** — This geometry minimizes electron pair repulsion between the two C=O bonds. • 💡 Wrong-option analysis: B: 90° is not found in simple molecules; C: 120° occurs in trigonal planar; D: 104.5° is for bent molecules like water.
Which of the following contains a double covalent bond?
Correct Answer: D. Oxygen (O₂)
• **Oxygen double bond** = Each oxygen atom shares two pairs of electrons to complete its outer shell, forming O=O. • **Stronger than single** — Double bonds are stronger and shorter than single bonds but weaker than triple bonds. • 💡 Wrong-option analysis: A: Chlorine has a single bond; B: Hydrogen has a single bond; C: Nitrogen has a triple bond.
When a metal reacts with a non-metal, the metal atom typically?
Correct Answer: A. Loses electrons and forms a cation
• **Electron loss** = Metals have low ionization energies and tend to lose valence electrons during chemical reactions easily. • **Cation formation** — By losing electrons, metals form positively charged ions called cations. • 💡 Wrong-option analysis: B: Metals don't always become noble gases; C: Non-metals gain electrons, not metals; D: Metals typically don't form covalent bonds with non-metals.
Which of the following is a non-polar molecule despite containing polar bonds?
Correct Answer: C. Carbon Tetrachloride (CCl₄)
• **CCl₄ symmetry** = Carbon tetrachloride is non-polar because its symmetrical tetrahedral shape causes the individual bond dipoles to cancel completely. • **Dipole cancellation** — All four C-Cl bond dipoles point toward the corner atoms, neutralizing each other. • 💡 Wrong-option analysis: A: NH₃ has asymmetric lone pair; B: H₂O is asymmetric with lone pairs; D: HF is strongly polar.
What name is given to the energy required to break one mole of a specific bond in a gaseous substance?
Correct Answer: A. Bond enthalpy
• **Bond enthalpy definition** = Bond enthalpy or bond energy measures the strength of a chemical bond between two atoms. • **Energy requirement** — Higher bond enthalpies indicate stronger, more stable bonds requiring more energy to break. • 💡 Wrong-option analysis: B: Ionization energy removes electrons from atoms; C: Lattice energy breaks ionic compounds; D: Activation energy starts reactions.
What is the hybridization of the carbon atom in an ethane (C₂H₆) molecule?
Correct Answer: A. sp³
• **sp³ hybridization** = Carbon in ethane forms four single sigma bonds, requiring sp³ hybridization with tetrahedral geometry. • **Orbital mixing** — One s orbital and three p orbitals combine to form four equivalent sp³ hybrid orbitals. • 💡 Wrong-option analysis: B: sp² produces trigonal planar; C: sp produces linear; D: sp³d requires more than four bonds.
Which of the following forces is the weakest?
Correct Answer: B. London dispersion forces
• **Dispersion force weakness** = London dispersion forces are temporary dipole-induced dipole attractions found in all molecules. • **Weakest interaction** — These forces depend on instantaneous electron distribution shifts and are the weakest intermolecular attraction. • 💡 Wrong-option analysis: A: Metallic bonds are strong; C: Ionic bonds are very strong; D: Covalent bonds are the strongest intramolecular forces.
According to the Octet Rule, how many electrons does a Magnesium atom (Atomic Number 12) lose to become stable?
Correct Answer: D. 2
• **Two electrons** = Magnesium has electron configuration 1s² 2s² 2p⁶ 3s² with two electrons in its outermost shell. • **Noble gas configuration** — After losing these two electrons, it achieves the stable neon configuration: Mg²⁺. • 💡 Wrong-option analysis: A: Magnesium doesn't lose three electrons; B: One electron leaves incomplete octet; C: Losing eight would make it unstable.