Metallic Bond Strength Across Period 3

Steps:

• Metallic melting points rise with stronger bonds between cations and delocalized electrons.
• From Na to Al, elements are in period 3: Na (group 1, +1 ion), Mg (+2), Al (+3).
• Ion charge increases from +1 to +3, enhancing electrostatic forces.
• This stronger attraction explains the melting point trend: Na (98°C) to Al (660°C).

Why A is correct:

• Higher ion charge increases electrostatic attraction to delocalized electrons, per metallic bonding model, raising bond strength and melting point.

Why the others are wrong:

• B: All these metals have delocalized electrons, but the statement doesn't specify an increase (from 1 to 3 electrons), so it fails to explain the trend.
• C: Ion radius decreases, increasing charge density, but charge increase is the dominant factor for this specific trend.

Final answer: A