The monomer of polyvinyl chloride (PVC) is: MCQ with Answer and Explanation

Explanation:
Magnesium (Z=12): configuration 2,8,2. Period = number of shells = 3; Group = 2 (2 valence electrons). Be is Group 2, Period 2; Ca is Group 2, Period 4; Sr Period 5.

Explanation:
Steel is an alloy of iron with controlled amounts of carbon (0.02-2.1%) and often other elements like manganese, chromium, nickel, etc. Cast iron contains 2-4% carbon. In steelmaking (Bessemer, LD process), impurities like excess carbon, silicon, manganese, sulfur, phosphorus are oxidized and removed, then desired carbon and alloying elements are added to achieve specific properties.

Explanation:
Burning of a candle involves combustion of wax (hydrocarbons) with oxygen to produce CO₂ and H₂O, a chemical change. The melting of wax is a physical change. Cutting wood is physical (size change). Freezing water is physical (state change). A chemical change results in new substances with different properties. Often irreversible.