Metallic bonding: a giant structure with mobile electrons
| English | 中文 | Pinyin |
|---|---|---|
| electrostatic attraction/ɪˌlektrəʊˈstætɪk əˈtrækʃn/ | 静电吸引 | jìng diàn xī yǐn |
| delocalised electron/dɪˈlɒkəlaɪzd ɪˈlektrɒn/ | 离域电子 | lí yù diàn zi |
What would explain this observation?
- A copper wire conducts as a solid. Unlike a solid ionic crystal, it already contains charge carriers that can move through its giant structure.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- A metal has a giant arrangement represented by positive metal ions in a sea of delocalised outer electrons. These electrons are not attached to one atom or one neighbouring pair and can move through the structure. Strong electrostatic attraction 静电吸引 between the positive ions and delocalised electrons 离域电子 is metallic bonding. The complete metal is electrically neutral: electron charge balances the positive charge represented by the ions.
- delocalised electron: An electron not attached to one atom or bond and able to move through the structure; electrostatic attraction: Attraction between opposite electrical charges.
Which particles carry current through a solid metal?
The shared electrons extend throughout the structure, so shifting layers can preserve attraction and allow bending. When a potential difference is applied, mobile electrons carry charge; the positive ions remain in their positions in a solid rather than drifting through the wire. The drawing’s ions and electron symbols are a model of the bulk bonding, not isolated metal ions mixed with a separate substance.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- The shared electrons extend throughout the structure, so shifting layers can preserve attraction and allow bending. When a potential difference is applied, mobile electrons carry charge; the positive ions remain in their positions in a solid rather than drifting through the wire. The drawing’s ions and electron symbols are a model of the bulk bonding, not isolated metal ions mixed with a separate substance.
- Compare a metallic diagram with an ionic lattice and a small covalent molecule. Identify whether electrons are local shared pairs or delocalised and whether both positive and negative ions are represented. Use school-approved low-voltage conductivity demonstrations, with no mains circuit and no heating of unknown samples. A schematic can show carriers but not their detailed motions or actual relative sizes.
Which two habits make the investigation or model in this case more defensible?
Compare a metallic diagram with an ionic lattice and a small covalent molecule. Identify whether electrons are local shared pairs or delocalised and whether both positive and negative ions are represented. Use school-approved low-voltage conductivity demonstrations, with no mains circuit and no heating of unknown samples. A schematic can show carriers but not their detailed motions or actual relative sizes.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: in a simplified sodium metal model, eight atoms each contribute one outer electron to the delocalised system. The model therefore has eight delocalised electrons balancing eight singly positive ion centres. A twelve-atom magnesium model contributes two each, giving twenty-four electrons. These are electron counts in an explicitly stated model, not a formula for every metal.
A stated magnesium model has ten atoms contributing two electrons each. How many electrons are delocalised? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
A stated magnesium model has ten atoms contributing two electrons each. How many electrons are delocalised?
The result is 20 electrons. Known: in a simplified sodium metal model, eight atoms each contribute one outer electron to the delocalised system. The model therefore has eight delocalised electrons balancing eight singly positive ion centres. A twelve-atom magnesium model contributes two each, giving twenty-four electrons. These are electron counts in an explicitly stated model, not a formula for every metal.
Check the conclusion and its limits
- The metal does not have a net positive charge simply because the drawing labels positive ion centres. Electrons are delocalised, not lost from the entire piece. Electrical conductivity in a solid metal is different from ion mobility in molten salt. Do not use the sodium model to assign one free electron to every metal atom universally.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
The positive ions make a complete metal electrically positive overall. This claim is false: The metal does not have a net positive charge simply because the drawing labels positive ion centres. Electrons are delocalised, not lost from the entire piece. Electrical conductivity in a solid metal is different from ion mobility in molten salt. Do not use the sodium model to assign one free electron to every metal atom universally.
Metallic bonding: a giant structure with mobile electrons: The shared electrons extend throughout the structure, so shifting layers can preserve attraction and allow bending. When a potential difference is applied, mobile electrons carry charge; the positive ions remain in their positions in a solid rather than drifting through the wire. The drawing’s ions and electron symbols are a model of the bulk bonding, not isolated metal ions mixed with a separate substance.
The positive ions make a complete metal electrically positive overall.
The metal does not have a net positive charge simply because the drawing labels positive ion centres. Electrons are delocalised, not lost from the entire piece. Electrical conductivity in a solid metal is different from ion mobility in molten salt. Do not use the sodium model to assign one free electron to every metal atom universally.
An electron not attached to one atom or bond and able to move through the structure: write the technical term.
delocalised electron means An electron not attached to one atom or bond and able to move through the structure.