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‘Using Models’: thread of ideas to develop pre-16 ideas about Structure & Bonding – Page 1
Level
Key idea
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Sorting objects into groups based on simple observations:
Group objects based on the physical properties (hard, soft etc.) of the materials they’re made from
Classify materials as ‘solid’, ‘liquid’ or ‘gas’ depending on physical properties.
Use simple models to represent materials and introduce scientific ideas:
- Describe states of matter in terms of the arrangement & motion of simple ‘particles’
Use simple models to explain observations or processes:
- change of state (s)  (l)  (g) requires heating
- particles in the solid & liquid states are attracted to each other
- energy transfer from the surroundings into the system is required to overcome these attractions (bonds)
Assess strengths & limitations of current simple particle model:
- (Strength). For pure substances, changes of state occur at fixed temperatures.
- (Limitation) Different substances undergo changes of state at different temperatures. The simple particle model
used so far does not yet take into account the differences in attraction (bonds) between different types of
particles.
Classify substances as elements, mixtures and compounds (e.g., different substances have different properties):
- Many different substances exist, formed from a relatively small number of elements
- Each element is made up of particles (atoms) unique to that element
- Atoms can combine in many different ways to form larger particles (e.g., molecules or giant structures)
- Compounds form when atoms of different elements combine
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Introduce a new, more complex model to explain further observations:
Periodic patterns: metals (m) & non-metals (nm), Group chem.
Atomic structure (atoms consist of a nucleus of protons & neutrons and electrons in shells)
How atoms react & can combine:
 sharing electrons to form covalent bonds ( molecules, giant covalent structures)
 transferring electrons to form oppositely charged ions which attract (giant structure of ions)
- Octet rule – atoms react “in order to fill up their outer electron shells”.
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➢ Assess strengths & limitations of current model:
- (Strengths): Different substances have different properties: melting point, boiling point, conductivity
- Similarity of Group chemistry
- Lines in emission spectra
- (Limitations): Unique line spectra patterns for different elements
- Trends in Group chemistry
- Spectra of metals  non-metal
- Trends: atomic radii, ionisation energies (IEs), electronegativities
- Properties of metals
- Reactions: elements (& compounds)
➢ Refine the model or devise a more complex model to explain further observations or data:
- It’s all electrostatic! (opposites attract)
- The nuclear atom (+ve protons, -ve electrons), core charge
- Attractions within an atom
 trends in atomic radii, IEs, electronegativities
- Spectrum of bonding
© Royal Society of Chemistry 2014
‘Using Models’: thread of ideas to develop pre-16 ideas about Structure & Bonding – Page 2
Level
Key idea
➢
Assess the strengths and limitations of the current model
(Strengths)
- Reactions of elements (& compounds)
- Attractions between atoms of different elements
- (m-m; m-nm; nm-nm)  spectrum of bonding
metallic bonds (+ve nucleus: delocalised electrons; non-directional)
ionic bonds (+ve ion; -ve ion; non-directional)
covalent bonds (+ve nucleus: localised electrons; directional)
- Explain the properties (melting point, boiling point, conductivity) of: metals; simple salts; some solids (giant
covalent), gases
(Limitations)
- Does not completely explain the properties of liquids and some solids (simple molecular/ macromolecular)
- Shapes of molecules
- Carbon chemistry
➢ Transition metal chemistry
© Royal Society of Chemistry 2014