The metallic model: notes and practice questions
- This topic explains the unique properties of transition metals, focusing on the role of delocalized d-electrons in metallic bonding.
- Transition elements exhibit high melting points and electrical conductivity.
- These properties are attributed to strong metallic bonds formed by both s and delocalized d-electrons.
- The less pronounced trend in melting points across the d-block is also considered.
How it is examined
Short. Usually one Paper 1A item on why metals conduct or why Mg melts higher than Na, and occasionally a 2-mark Paper 2 explanation. The malleability explanation wants layers of cations sliding while the delocalized electrons keep the attraction intact; "the atoms can move" does not earn it.
Ionic radii and melting points. The model itself is recall.
- 2.3.1 A metallic bond is the electrostatic attraction between a lattice of cations and delocalized electrons. Students explain the electrical conductivity, thermal conductivity and malleability of metals.
- 2.3.2 The strength of a metallic bond depends on the charge of the ions and the radius of the metal ion. Students explain trends in melting points of s and p block metals.
Guiding questions
- What determines the metallic nature and properties of an element?
Linking questions
- Tool 1, Inquiry 2, Structure 3.1 What experimental data demonstrate the physical properties of metals, and trends in these properties, in the periodic table?
- Reactivity 3.2 What trends in reactivity of metals can be predicted from the periodic table?
- Structure 2.4 What are the features of metallic bonding that make it possible for metals to form alloys?
- Structure 3.1 (HL) Why is the trend in melting points of metals across a period less evident across the d-block?
Practice questions
5 questions · 1 easy · 3 medium · 1 hardQuestion 1
EasyPaper 1A · calculator1 markWhich statement explains why copper can be drawn into wires without breaking?
A. Layers of positive ions can slide past each other while the delocalized electrons maintain the metallic bond.
B. Positive ions are free to move throughout the structure when a tensile force is applied.
C. Metallic bonds are directional, allowing atoms to shift easily into new fixed orientations.
D. Repulsion between delocalized electrons pushes the metal ions into elongated shapes.
Think about the arrangement of particles in a metallic lattice. When an external force is applied, how do the layers of cations behave relative to the delocalized electron cloud?
Question 2
MediumPaper 1A · calculator1 markWhich of the following metals has the highest melting point?
A. Sodium
B. Potassium
C. Magnesium
D. Aluminium
Consider how the charge of the metal cation and its ionic radius affect the strength of the electrostatic attraction to the delocalized electrons across Period 3 and down Group 1.
Question 3
HardPaper 2 · calculator3 marksThe melting points of potassium and vanadium are and , respectively.
Explain why the melting point of vanadium is significantly higher than that of potassium.
Consider the factors that determine the strength of metallic bonding: the charge on the cations, the ionic radius, and which electrons are involved in the delocalized 'sea' of electrons.
Question 4
MediumPaper 1A · calculator1 markWhich statement correctly compares the metallic bonding in titanium to that in calcium?
A. Titanium has stronger metallic bonding because both 3d and 4s electrons can be delocalized into the electron sea.
B. Titanium has weaker metallic bonding because 3d electrons shield the outer valence electrons from the nucleus.
C. Calcium has stronger metallic bonding because its valence electrons require less energy to remove.
D. Calcium has stronger metallic bonding because its cations have a higher charge density.
Consider the electron configurations of both elements and which electrons participate in the metallic bond for transition metals compared to s-block metals.
Question 5
MediumPaper 2 · calculator4 marksCopper is a transition metal widely utilized in plumbing and manufacturing due to its malleability.
(a) Outline the metallic bonding model in copper in terms of the particles present and the electrostatic attraction.
(b) Describe how this metallic bonding model accounts for the malleability of copper when an external mechanical force is applied.
Consider the two types of charged species present in a metallic lattice and the electrostatic interaction that holds them together.
Consider how the arrangement of cations changes under applied stress, how the delocalized electrons respond, and why the bonding is not broken as a result.
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Where marks are lost
- Reaching for "human error" or "only one trial." A source of error has to be a specific step in the method, not a general apology for the result.
- Joining the dots instead of drawing a curve.
- Naming a chemical instead of the property that distinguishes it, or vice versa. Answering with the nearest fact that comes to mind rather than the fact the command term and stem jointly ask for is a recurring way to answer a question that was not, quite, the one asked.
