Bonding & Structure Flashcards
(24 cards)
Describe the arrangement and movement of particles in a solid.
In a solid, particles are tightly packed in a regular lattice and can only vibrate about fixed positions. This gives solids a definite shape and volume, and they are incompressible.
Describe the arrangement and movement of particles in a liquid.
In a liquid, particles are close together but can slide past each other, allowing liquids to flow and take the shape of their container. Liquids have a fixed volume but no fixed shape.
Describe the arrangement and movement of particles in a gas.
In a gas, particles are far apart and move randomly at high speeds. Gases have neither a fixed shape nor fixed volume, filling any container they occupy and are easily compressible.
Explain what happens at the melting and boiling points.
At the melting point, a solid absorbs enough energy to overcome forces holding its particles in place and becomes a liquid. At the boiling point, a liquid absorbs enough energy for particles to break free into a gas. Both are physical, reversible changes.
Outline the structure of an atom.
An atom consists of a tiny central nucleus containing positively charged protons and neutral neutrons, surrounded by negatively charged electrons in energy levels (shells). The number of protons (atomic number) defines the element.
Define an ion and explain how ionic bonds form.
An ion is a charged particle formed when an atom loses or gains electrons. Ionic bonds form when a metal atom loses electrons to become a positive ion and a non‑metal gains electrons to become a negative ion; the opposite charges attract.
Describe the structure of a giant ionic lattice.
In a giant ionic lattice, each positive ion is surrounded by negative ions and vice versa in a repeating 3D pattern. This strong electrostatic attraction in all directions gives ionic compounds high melting and boiling points.
List three properties of ionic compounds and explain why.
1) High melting/boiling points: strong ionic bonds require lots of energy to break. 2) Conduct electricity when molten or dissolved: ions are free to move and carry charge. 3) Hard but brittle: lattice layers slip and like charges repel, causing shattering.
Define covalent bonding.
Covalent bonding is the sharing of pairs of electrons between non‑metal atoms, so each atom achieves a full outer shell of electrons. The shared electrons are attracted by both nuclei, holding the atoms together.
Give two examples of simple molecular substances and their properties.
Examples: water (H₂O) and carbon dioxide (CO₂). They have low melting/boiling points due to weak intermolecular forces, are often gases or liquids at room temperature, and do not conduct electricity.
Explain the structure and properties of diamond.
Diamond is a giant covalent structure where each carbon atom forms four strong covalent bonds in a tetrahedral lattice. It is extremely hard, has a very high melting point, and does not conduct electricity.
Explain the structure and properties of graphite.
Graphite consists of layers of hexagonally arranged carbon atoms, each bonded to three others, with one delocalised electron per atom between layers. It is soft (layers slide), conducts electricity, and has a high melting point.
Define metallic bonding and describe its main features.
Metallic bonding occurs between metal atoms: outer electrons become delocalised, forming a ‘sea of electrons’ around positive metal ions. This gives metals their conductivity, malleability, and high melting points.
Explain why metals are good conductors of heat and electricity.
In metals, delocalised electrons can move freely and carry charge (electrical conductivity). They also transfer kinetic energy rapidly through the electron ‘sea,’ making metals good thermal conductors.
What is an alloy and why are they used + examples?
An alloy is a mixture of a metal with one or more other elements, designed to disrupt the regular lattice of pure metal, making it harder or more resistant to corrosion. Examples include steel (iron + carbon) and bronze (copper + tin).
Define a polymer and describe how it is formed.
A polymer is a large molecule made by joining many small repeating units (monomers) via covalent bonds in a process called polymerisation. Polymers can be natural (e.g. DNA) or synthetic (e.g. plastics).
Compare the melting points of polymers and giant covalent substances.
Polymers generally have lower melting points than giant covalent substances (like diamond) because they have weaker intermolecular forces (vanderWaals) between chains rather than covalent bonds throughout. Hence, it takes more energy to overcome the intermolecular forces between the bonds of giant covalent substances in comparison to polymers.
Define nanoparticles and give their size range.
Nanoparticles are extremely small particles with at least one dimension between 1 and 100 nanometres. Because of their size, they have a very high surface-area-to-volume ratio, giving them unique properties.
Give two applications of nanoparticles.
1) Medicine: targeted drug delivery using nanoparticle carriers. 2) Sunscreens: nanoparticles of zinc oxide or titanium dioxide block UV rays more effectively while remaining transparent on skin.
Mention two potential risks of nanoparticles.
1) Health: they can enter cells and cause unknown toxic effects. 2) Environment: they may accumulate in water or soil, disrupting ecosystems.
Explain how bonding type affects melting and boiling points.
Stronger bonds or forces between particles (ionic bonds, covalent bonds in giant structures, metallic bonds) require more energy to break, resulting in higher melting and boiling points compared to weak intermolecular forces.
Describe when ionic compounds conduct electricity and why.
Ionic compounds conduct electricity only when molten or dissolved in water because ions are then free to move and carry electric charge; in the solid state, ions are fixed in the lattice and cannot move.
Explain why most covalent compounds do not conduct electricity.
In covalent compounds, electrons are localised in bonds and there are no free charged particles, so they cannot carry electric current (graphite is the exception because of delocalised electrons).
State three uses of polymers and one advantage of each.
1) Plastic bottles: lightweight and shatterproof. 2) Nylon (clothing): strong and elastic. 3) Poly(ethene) bags: flexible and cheap to produce.
