Electrical conductivity trend in Period 3 elements

Steps:

• Identify Period 3 elements: Na, Mg, Al (metals, high conductivity), Si (semimetal, moderate), P, S, Cl (nonmetals, low), Ar (insulator, none).
• Recall trend: Conductivity decreases left to right as metallic bonding weakens and covalent/ionic character increases, reducing delocalized electrons.
• Evaluate options by comparing relative orders to this trend (e.g., Na > Mg > Si for metals/semimetal).
• Select option matching highest conductivity for metals, lowest for nonmetals.

Why B is correct:

• B accurately orders sets with metals > semimetals > nonmetals, aligning with metallic character decreasing across the period per periodic trends.

Why the others are wrong:

• A reverses metal/nonmetal order, ignoring increasing nonmetallic character.
• C misplaces Si as high conductivity, but it's a poor conductor compared to metals.
• D equates all nonmetals' low conductivity incorrectly, overlooking slight variations.

Final answer: B