In metallic solid, the forces of attraction is between the mobile valence electrons and the

Analyze the question: It asks what the mobile valence electrons in a metal are attracted to. This is about metallic bonding.

Concept: In a metallic solid, the metal atoms lose their outer (valence) electrons. These electrons become delocalised and form a "sea" of mobile electrons. What remains are positive metal ions (kernels), which are the nuclei plus the inner electrons. Metallic bonding is the electrostatic attraction between the sea of delocalised electrons and these positively charged ions or nuclei.

Solution:

• A. Atoms: Atoms are neutral overall, and the metal atoms have in effect become positive ions, so this is not the best description.
• B. Neutrons: Neutrons have no charge, so they cannot attract electrons.
• C. Negative ions: Electrons would be repelled by negative ions, so this is wrong.
• D. Positively charged nuclei: The positive metal ions (nuclei with inner shells) attract the mobile electrons. This is correct.

Answer: D, positively charged nuclei

Exam tip: Remember "metal = positive ions in a sea of electrons." Opposite charges attract, so the electrons must be attracted to something positive. Always eliminate neutral (neutrons) and negative options first.