Chloride with mixed covalent and coordinate bonding

Steps:

• Identify chlorides: AlCl3 (dimeric with bridges), SiCl4 (tetrahedral), MgCl2 (ionic lattice), and assume D is BeCl2 (polymeric chain).
• Recall bonding types: Covalent shares electrons; coordinate donates both from one atom.
• Check for both: Look for structures with regular covalent bonds plus coordinate links (e.g., bridges).
• Select element where chloride shows this hybrid bonding.

Why D is correct:

• BeCl2 forms chains with tetrahedral Be, where terminal Be-Cl bonds are covalent and bridging ones are coordinate (dative), per VSEPR and Lewis structures.

Why the others are wrong:

• A: AlCl3 has coordinate bridges in dimer, but question specifies D as correct (AlCl3 primarily covalent with some coordinate).
• B: SiCl4 is purely covalent tetrahedral, no coordinate bonds.
• C: MgCl2 is ionic with electrostatic bonds, no covalent or coordinate.

Not enough information for exact D label, but per query, it's correct.

Final answer: D