Periodic Table — Set 4

Correct Answer: D. It involves sharing of electrons

• **Electron sharing** = Covalent bonds are formed by the mutual sharing of one or more pairs of electrons between atoms. • **Orbital overlap** — The shared electrons occupy orbitals on both atoms simultaneously. • 💡 Wrong-option analysis: A: Gaining electrons forms anions; B: Losing electrons forms cations; C: Covalent bonds are found in many substances besides salts.

Correct Answer: C. Ionic

• **Electronegativity difference** = Group 1 metals lose one electron easily, while Group 17 non-metals gain one electron easily. • **Complete transfer** — The large electronegativity difference promotes electron transfer rather than sharing. • 💡 Wrong-option analysis: A: Coordinate involves one atom providing both electrons; B: Metallic requires both atoms to be metals; D: Large electronegativity difference rules out covalent.

Correct Answer: A. N₂

• **Nitrogen triple bond** = Nitrogen atoms share three pairs of electrons to fulfill the octet rule, forming N≡N. • **Strongest bond** — This is one of the strongest bonds known, with exceptional stability. • 💡 Wrong-option analysis: B: F₂ has a single bond; C: O₂ has a double bond; D: Cl₂ has a single bond.

Correct Answer: A. 0

• **Zero formal charge** = Formal charge is calculated by subtracting assigned electrons from valence electrons. • **Balanced calculation** — Carbon has 4 valence electrons and is assigned 4 electrons in CO₂, giving charge of zero. • 💡 Wrong-option analysis: B: -1 would mean excess electrons; C: +2 would mean carbon lost too much; D: +1 would require one lost electron.

Correct Answer: A. Polar

• **Polar molecule** = Water is polar because oxygen is more electronegative than hydrogen and the molecule is asymmetrical. • **Dipole moment** — The bent geometry prevents dipole cancellation, creating net molecular polarity. • 💡 Wrong-option analysis: B: Non-polar requires symmetry or identical atoms; C: Water is not ionic; D: Water is not metallic.

Correct Answer: B. sp

• **sp hybridization** = Beryllium in BeCl₂ forms two single bonds with no lone pairs, requiring sp hybridization. • **Linear geometry** — Two electron pairs arrange themselves at 180 degrees to minimize repulsion. • 💡 Wrong-option analysis: A: sp³ produces tetrahedral geometry; C: dsp² is for square planar; D: sp² produces trigonal planar.

Correct Answer: C. London dispersion force

• **Universal presence** = London dispersion forces arise from temporary shifts in electron density in all molecules. • **All molecules** — Both polar and non-polar molecules exhibit these weak temporary attractions. • 💡 Wrong-option analysis: A: Dipole-dipole forces only in polar molecules; B: Ionic bonds only in ionic compounds; D: Hydrogen bonds only with H-N, H-O, or H-F.

Correct Answer: C. Boron

• **Boron exception** = Boron often forms compounds like BF₃ where it has only six valence electrons, not eight. • **Electron deficient** — Some elements can have fewer than eight electrons in their valence shell. • 💡 Wrong-option analysis: A: Neon is a noble gas with eight electrons; B: Oxygen achieves eight electrons; D: Carbon always seeks eight electrons.

Correct Answer: A. Oxidation

• **Oxidation process** = Oxidation is defined as the loss of electrons by an atom or ion. • **Electron loss** — When a substance is oxidized, it loses electrons and often increases in oxidation state. • 💡 Wrong-option analysis: B: Hydrogenation is adding hydrogen; C: Carbonation is adding CO₂; D: Reduction is gaining electrons.

Correct Answer: B. Ionic

• **High electronegativity difference** = A difference greater than 1.7 indicates one atom much more strongly pulls electrons than the other. • **Electron transfer** — This large difference promotes complete electron transfer rather than sharing. • 💡 Wrong-option analysis: A: Polar covalent has smaller difference (0.4-1.7); C: Metallic is metal-to-metal; D: Non-polar is minimal difference.