Nitrogen molecule (N₂) has a triple bond between the two nitrogen atoms (N≡N), with bond order 3. This makes it very stable and relatively inert. O₂ has a double bond (O=O). CH₄ has four single C–H bonds. H₂O has two single O–H bonds. The triple bond in N₂ requires high energy to break, which is why N₂ is used as an inert atmosphere. Bond energy N≡N ≈ 946 kJ/mol.
Explanation:
Wood has lower calorific value (~17 kJ/g) compared to coal (~25-35 kJ/g), methane (~55.5 kJ/g), and hydrogen (~142 kJ/g). It contains moisture and oxygen, reducing energy density.
Explanation:
Atomic radius increases down a group as the number of shells increases. Iodine (I) is in Period 5, below F (2), Cl (3), Br (4). Thus iodine has the largest atomic radius among these halogens.
Explanation:
Iodine directly converts from solid to violet vapor on gentle heating (sublimation). NaCl melts; sugar decomposes; copper melts at high temperature. Other sublimable substances: camphor, naphthalene, dry ice.
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