The metallic model practice questions.

Which statement correctly describes the metallic model of bonding?

• Cations in a lattice surrounded by a sea of delocalised electrons
• Anions held together by shared electron pairs
• Alternating positive and negative ions arranged within a giant ionic lattice
• Neutral atoms held by weak London dispersion forces

Answer: Cations in a lattice surrounded by a sea of delocalised electrons

Metallic bonding is the electrostatic attraction between a lattice of metal cations and the delocalised (mobile) valence electrons.

Which factors lead to the strongest metallic bonding?

• Low cation charge and few delocalised electrons
• Large metallic radius and low cation charge
• High cation charge and small metallic radius
• High cation charge and large metallic radius

Answer: High cation charge and small metallic radius

Stronger metallic bonding results from a greater charge on the cation, a smaller radius, and more delocalised electrons per atom.

Which metal is expected to have the strongest metallic bonding and highest melting point?

• Sodium (Na)
• Magnesium (Mg)
• Aluminium (Al)
• Potassium (K)

Answer: Aluminium (Al)

Aluminium provides three delocalised electrons per atom and forms Al³⁺, giving the strongest attraction of these period-3/group-1 metals.

Explain why metals are malleable and ductile.

• Covalent bonds break and reform easily
• Layers of cations can slide over one another while the delocalised electrons maintain the bonding
• The lattice contains no directional bonding at all, so the atoms are able to move around completely freely
• Like-charged ions repel when displaced

Answer: Layers of cations can slide over one another while the delocalised electrons maintain the bonding

When force is applied, layers of cations slide past each other; the non-directional sea of electrons keeps the metallic bonding intact, so the metal deforms without shattering.

Why can metals conduct electricity in both the solid and molten states?

• They contain freely mobile positive ions that carry the charge in both states
• They contain delocalised electrons that are free to move in both states
• Their covalent bonds carry charge
• Heating creates new charge carriers

Answer: They contain delocalised electrons that are free to move in both states

Unlike ionic compounds, metals have delocalised valence electrons that are mobile whether the metal is solid or molten, so they conduct in both states.

Across period 3 from sodium to aluminium, how does the melting point of the metals change and why?

• Decreases steadily, because the atomic radius of the metal atoms increases across the period
• Increases, because the charge on the cation and number of delocalised electrons increase
• Stays constant, because all are metals
• Decreases, because delocalised electrons decrease

Answer: Increases, because the charge on the cation and number of delocalised electrons increase

From Na to Al the cation charge rises (1+ to 3+) and more electrons are delocalised, strengthening metallic bonding and raising the melting point.