i NaCl: Ionic solidReasoning: NaCl is composed of a metal sodium, Na and a non-metal chlorine, Cl . In ionic compounds, metals lose electrons to form positive ions cations , while non-metals gain electrons to form negative ions anions . In NaCl, sodium loses one electron to form Na+ and chlorine gains one electron to form Cl-. The electrostatic attraction between these oppositely charged ions forms an ionic bond, resulting in an ionic solid. ii CO2: Covalent solidReasoning: CO2 is composed of non-metal elements carbon, C, and oxygen, O . In covalent compounds, non-metal atoms share electrons to form covalent bonds. In CO2, carbon shares electrons with two oxygen atoms, forming a covalent bond with each. The solid form of CO2, known as dry ice, consists of CO2 molecules held together by weak intermolecular forces, making it a covalent solid. iii Fe: Metallic solidReasoning: Fe is a pure metal iron . In metallic solids, metal atoms are arranged in a lattice structure, and their valence electrons are delocalized, forming a "sea of electrons" that can move freely throughout the structure. This delocalization of electrons results in strong metallic bonds, making Fe a metallic solid. iv SiO2: Covalent solidReasoning: SiO2 is composed of non-metal elements silicon, Si, and oxygen, O . In covalent compounds, non-metal atoms share electrons to form covalent bonds. In SiO2, each silicon atom is bonded to four oxygen atoms, and each oxygen atom is bonded to two silicon atoms, forming a three-dimensional network of covalent bonds. This extensive covalent bonding makes SiO2 a covalent solid. v Ag: Metallic solidReasoning: Ag is a pure metal silver . In metallic solids, metal atoms are arranged in a lattice structure, and their valence electrons are delocalized, forming a "sea of electrons" that can move freely throughout the structure. This delocalization of electrons results in strong metallic bonds, making Ag a metallic solid.