Bonding, structure and the properties of matter

• Three bonds hold matter together: ionic (transferred electrons, charged ions), covalent (shared electron pairs) and metallic (delocalised electrons).
• Structure follows bonding: giant ionic lattices, small molecules, polymers, giant covalent structure networks and metal lattices — each predicts melting point and conductivity.
• Carbon shows every trick: diamond, graphite, graphene, fullerenes; nanoparticles (chemistry only) turn surface area into properties.

Three strong chemical bonds, all explained by electrostatic forces:

• Ionic 离子键 — a metal atom transfers outer electrons to a non-metal: metal atoms lose electrons to become positive ions; non-metal atoms gain them to become negative ions; Groups 1/2 metals and 6/7 non-metals form ions with noble-gas electronic structures. Draw the electron transfer with dot and cross diagrams; deduce ion charges from group number (Group 1 → +1, Group 2 → +2, Group 6 → −2, Group 7 → −1).
• Covalent 共价键 — non-metal atoms share pairs of electrons. Know dot-and-cross diagrams for H₂, Cl₂, O₂, N₂, HCl, H₂O, NH₃, CH₄, and line representations for small molecules, polymer repeating units and giant covalent structures.
• Metallic 金属键 — a giant lattice of metal atoms with delocalised outer electrons 游离电子 free to move through the whole structure; the sharing of these electrons gives strong metallic bonding.

Know the limitations of models: dot-and-cross, ball-and-stick, 2D and 3D diagrams all simplify — no forces shown, fixed bond lengths, giant structures drawn as small fragments. Deduce empirical formulae from lattice models; molecular formulae from molecule diagrams.

States of matter: solid, liquid, gas; melting/freezing at the melting point, boiling/condensing at the boiling point. Particle theory (small solid spheres) explains the changes; the stronger the forces between particles, the higher the melting/boiling points. (HT) The simple model's limits: no forces shown, all spheres, solid particles. State symbols: (s), (l), (g), (aq).

Larger molecules → stronger intermolecular forces → higher melting/boiling points. Alloys 合金 are harder than pure metals because different-sized atoms distort the layers, stopping them sliding.

• Diamond — a giant covalent structure 巨型共价结构 in which each carbon forms four covalent bonds: very hard, very high melting point, does not conduct.
• Graphite — each carbon forms three bonds, layers of hexagonal rings with no covalent bonds between layers (soft, slippery — lubricant); one delocalised electron per atom → conducts electricity like a metal.
• Graphene — a single layer of graphite: one atom thick, strong, conducts — electronics and composites.
• Fullerenes — hollow molecules of carbon hexagons (plus 5- or 7-membered rings); Buckminsterfullerene C₆₀ 富勒烯 is spherical. Carbon nanotubes 碳纳米管 — cylindrical fullerenes with huge length-to-diameter ratios: nanotechnology, electronics, materials.

Nanoscience = structures 1–100 nm (a few hundred atoms). Nanoparticles 纳米颗粒 are smaller than fine particles (PM2.5, 100–2500 nm), which are smaller than coarse particles/dust (PM10, 1 × 10⁻⁵–2.5 × 10⁻⁶ m).

Surface area : volume: as a cube's side decreases 10×, SA:V increases 10×. Nanoparticles may have different properties from the bulk material because of this high ratio — catalysts (smaller quantities work), medicine delivery, cosmetics, electronics. Concerns: effects inside the body and in the environment are not fully known.

• The three bonds in terms of electrons and electrostatic forces; ion charges from group numbers.
• Dot-and-cross for the eight named molecules; model limitations named.
• The properties table above rebuilt from memory — which forces are overcome on melting.
• Diamond vs graphite vs graphene vs fullerenes, bonding to property.
• (Chem) SA:V factor-of-10 rule; the three particle-size bands and nanoparticle uses and concerns.