IB DP Chemistry -Structure 2.3 The metallic model - IB Style Questions For SL Paper 1A -FA 2025
▶️ Answer/Explanation
All these metals are in Group 2. Metallic bonding strength generally decreases down a group because the atomic radius increases, resulting in a weaker attraction between the delocalized electrons and the metal cations. Magnesium, being the smallest and having the highest charge density, has the strongest metallic bonding.
✅ Answer: (A)
▶️ Answer/Explanation
Group 1 metals form metallic bonds, which depend on the attraction between positive metal ions and delocalized electrons.
As you go down group 1:
• the metal ion radius increases,
• the distance between the nuclei and the delocalized electrons becomes larger,
• metallic bonding becomes weaker.
Weaker metallic bonding means less energy is required to break the lattice, so the melting point decreases.
Therefore, the correct explanation is that the radius of the metal ion increases.
✅ Answer: (C)
▶️ Answer/Explanation
Metals consist of a regular lattice of positive metal ions surrounded by a sea of delocalized electrons.
• The metal atoms lose their valence electrons, forming positive ions.
• These delocalized electrons move freely and are responsible for conductivity, but they are not negative ions.
• There are no negative ions or molecules in a metallic lattice.
Therefore, the only particles present in the metal lattice are positive ions (and delocalized electrons).
✅ Answer: (C)
▶️ Answer/Explanation
Metals in group 1 (Li, Na, K, Rb) all form +1 ions and have one delocalized electron per atom, so the main factor affecting metallic bond strength is the size of the metal ion.
• A smaller metal ion has a higher charge density and can attract the sea of delocalized electrons more strongly.
• Going down the group from Li → Na → K → Rb, the ionic radius increases, so the attraction between positive ions and delocalized electrons becomes weaker and metallic bonds become weaker.
Lithium has the smallest ion and therefore the strongest metallic bonding of the options given.
✅ Answer: A