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VCE Chemistry Unit 1 AOS 1
The Atom: The Fundamental Building Block
All matter is made of atoms. An element’s identity is defined by its atomic number (Z), the number of protons in its nucleus. Its chemical behavior is determined by its valence electrons—the electrons in its outermost shell.
Nucleus (p+, n)
- Protons (+): Positively charged particles in the nucleus. Define the element.
- Neutrons (n): Neutral particles in the nucleus. Variations create isotopes.
- Electrons (-): Negatively charged particles orbiting the nucleus in shells. Valence electrons determine reactivity.
Key Idea: The arrangement of electrons, especially the valence electrons, dictates how atoms interact.
The Periodic Table & Electronegativity
The periodic table arranges elements to reveal patterns in their properties. Electronegativity, the ability of an atom to attract bonding electrons, is a key trend that predicts the type of bond that will form.
Chemical Bonding: The Forces Between Atoms
The difference in electronegativity between atoms determines how they bond. This, in turn, dictates a material’s entire set of properties. Explore the main types of primary bonding below.
Key Properties
Metals & Alloys
The metallic bonding model explains the unique properties of metals. Modifying the pure metallic lattice by creating alloys allows us to engineer materials with specific, enhanced properties.
Pure Metals
A regular lattice of cations in a “sea” of delocalised electrons. The layers of ions can slide past one another easily.
- ✅ Malleable & Ductile
- ✅ Excellent Conductors
- ✅ Lustrous
Alloys
A mixture containing a metal and at least one other element. Different sized atoms disrupt the lattice layers.
- ❌ Less Malleable (Harder)
- ✅ Still Conductive
- ✅ Often Stronger & More Corrosion-Resistant
Ionic Compounds: Hard but Brittle
Ionic compounds form rigid crystal lattices. While the strong ionic bonds make them hard, a sharp force can cause the lattice to shatter. This interactive model shows why.
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Click the button to apply force to the crystal.
Covalent Molecular Substances
Covalent substances consist of discrete molecules. Their properties are governed by the weak forces *between* molecules (intermolecular forces), not the strong covalent bonds *within* them. This leads to low melting points and no electrical conductivity.
Dispersion Forces
Weakest force, present in all molecules. Arises from temporary electron cloud fluctuations.
Dipole-Dipole Forces
Occurs between polar molecules due to permanent partial charges.
Hydrogen Bonding
Strongest type. Occurs when H is bonded to N, O, or F. Crucial for water’s properties.
The Allotropes of Carbon: Structure is Everything
Diamond and graphite are both pure carbon, yet their properties are opposites. This is the ultimate proof that the arrangement of atoms (structure) determines the properties of a material.
Diamond
A rigid 3D tetrahedral network.
- Hardness: Extremely Hard
- Conductivity: Insulator
- Structure: All electrons are in strong, localized covalent bonds.
Graphite
2D layers held by weak forces.
- Hardness: Soft & Slippery
- Conductivity: Conductor
- Structure: Has mobile, delocalised electrons within its layers.
Essential Lab Techniques
Practical skills are key in chemistry. Chromatography separates mixtures based on component properties, while flame tests identify metal ions by the unique color of light they emit when heated.
Paper Chromatography
Separates pigments based on their solubility in the solvent and attraction to the paper.
Flame Tests
Click to test different metal ions.
Sustainable Chemistry
Modern chemistry aims to create a circular economy, moving away from a “take-make-dispose” model. This is guided by the principles of Green Chemistry, which seek to reduce waste and environmental harm at a molecular level.
