Periodic Table — Set 1
Chemistry · आवर्त सारणी · Questions 1–10 of 40
Which type of chemical bond involves the complete transfer of electrons from one atom to another?
Correct Answer: B. Ionic bond
• **Ionic bond definition** = An ionic bond forms when one atom completely gives up electrons to another, creating charged ions. • **Electron transfer** — This is characteristic of bonding between metals (low electronegativity) and non-metals (high electronegativity). • 💡 Wrong-option analysis: A: Metallic bonds involve a sea of delocalized electrons; C: Covalent bonds involve sharing, not transfer; D: Hydrogen bonds are weak dipole attractions.
What is the primary reason why atoms form chemical bonds with each other?
Correct Answer: B. To achieve a stable octet configuration
• **Octet goal** = Atoms bond to reach a more stable state by filling their outermost electron shell with eight electrons. • **Noble gas configuration** — Most atoms seek to match noble gas configurations which are highly stable. • 💡 Wrong-option analysis: A: Bonding typically reduces reactivity, not increases it; C: Chemical bonding doesn't change atomic mass; D: Bonding doesn't inherently increase kinetic energy.
Which of the following molecules contains a triple covalent bond?
Correct Answer: B. Nitrogen (N₂)
• **Nitrogen triple bond** = N₂ has nitrogen atoms sharing three pairs of electrons forming a very strong triple bond. • **Strong connection** — This triple bond makes atmospheric nitrogen relatively unreactive and difficult to separate. • 💡 Wrong-option analysis: A: Methane has four single C-H bonds; C: Oxygen has a double bond; D: Water has two single O-H bonds.
What type of bond is formed when atoms share electrons equally between them?
Correct Answer: D. Non-polar covalent bond
• **Non-polar definition** = Non-polar covalent bonds occur when two atoms with similar electronegativities share electrons equally. • **Even distribution** — Neither atom has a stronger pull on the shared electron pair. • 💡 Wrong-option analysis: A: Electrovalent bonds involve complete electron transfer; B: Polar covalent bonds involve unequal sharing; C: Coordinate bonds have both electrons from one atom.
The 'Sea of Electrons' model is used to describe the bonding in which type of substances?
Correct Answer: D. Metals
• **Metallic bonding model** = Metallic bonding involves a lattice of positive ions surrounded by a mobile cloud of delocalized electrons. • **Free electron movement** — These electrons move freely throughout the structure, giving metals their electrical and thermal conductivity. • 💡 Wrong-option analysis: A: Ionic crystals use electrostatic attraction; B: Covalent solids have localized electron pairs; C: Noble gases are inert and don't form bonds.
Which of these bonds is characterized by the sharing of an electron pair where both electrons come from the same atom?
Correct Answer: C. Coordinate covalent bond
• **Coordinate bond uniqueness** = One atom provides both electrons for the shared pair while the other provides none. • **Dative bonding** — Also called a dative bond, it's common in coordination complexes and in molecules like ammonia forming ammonium ion. • 💡 Wrong-option analysis: A: Double bonds have equal electron contribution from both atoms; B: Metallic bonds involve electron seas; D: Ionic bonds involve complete transfer.
Which intermolecular force is responsible for the unexpectedly high boiling point of water?
Correct Answer: B. Hydrogen bonding
• **Hydrogen bond strength** = Hydrogen bonding is a strong dipole-dipole attraction occurring when hydrogen is bonded to highly electronegative elements like oxygen, nitrogen, or fluorine. • **Exceptional case** — Water's high boiling point compared to other similar compounds is due to extensive hydrogen bonding networks. • 💡 Wrong-option analysis: A: Covalent attractions don't operate between molecules; C: Water is not ionic; D: Van der Waals forces are much weaker than hydrogen bonds.
What is the shape of a methane (CH₄) molecule according to the VSEPR theory?
Correct Answer: B. Tetrahedral
• **Tetrahedral geometry** = Methane adopts a tetrahedral shape because four pairs of bonding electrons repel each other into this 3D arrangement. • **Bond angle** — The four C-H bonds are arranged at approximately 109.5 degrees to each other. • 💡 Wrong-option analysis: A: Octahedral is for six electron pairs; C: Trigonal planar is for three electron pairs; D: Linear is for two electron pairs.
Which property is generally characteristic of ionic compounds?
Correct Answer: B. High melting and boiling points
• **High melting points** = Ionic compounds have high melting and boiling points due to strong electrostatic forces holding the lattice together. • **Lattice strength** — These strong attractions require significant energy to overcome during melting or boiling. • 💡 Wrong-option analysis: A: Ionic compounds have very high melting points; C: Solids don't conduct due to fixed ions; D: Ionic compounds dissolve in polar, not non-polar solvents.
Which of the following elements has the highest electronegativity on the Pauling scale?
Correct Answer: A. Fluorine
• **Fluorine supremacy** = Fluorine is the most electronegative element with a value of 4.0 on the Pauling scale. • **Strongest attraction** — It has the strongest tendency to attract shared electrons in any chemical bond. • 💡 Wrong-option analysis: B: Carbon has 2.5 electronegativity; C: Oxygen is 3.4, less than fluorine; D: Cesium is extremely low at 0.8.