The compound CH₃CH₂OH is commonly known as: MCQ with Answer and Explanation

Explanation:
Across period 3, nuclear charge increases (Na: 11+, Cl: 17+) while electrons are added to the same shell. The increased attraction pulls electrons closer, decreasing radius. Na has larger radius despite having fewer electrons.

Explanation:
Henry Moseley discovered that the atomic number (number of protons) is the fundamental property of an element, not atomic mass. He proposed the modern periodic law: properties are periodic functions of atomic numbers. Mendeleev's law was based on atomic mass, which had anomalies.

Explanation:
Highly reactive metals (K, Na, Ca, Mg, Al) are extracted by electrolysis of their fused (molten) salts because chemical reducing agents cannot reduce their ores. For sodium, Down's process: electrolysis of molten NaCl with CaCl₂ to lower melting point. Iron is extracted by smelting (blast furnace). Copper and zinc can be extracted by reduction with coke or electrolytic refining of impure metal.