Bonding, structure and the properties of matter - Flashcards

This set covers ionic and covalent bonding, types of structures, properties of different substance types (ionic, molecular, giant covalent, metallic), carbon allotropes, polymers, nanoscience, and related concepts from the notes.

What is ionic bonding?

The electrostatic attraction between positive and negative ions.

Define a giant lattice.

A regular structure containing a massive number of ions/particles that extends in all directions.

Why do ionic substances have high melting and boiling points?

Because strong electrostatic forces between the ions require a lot of energy to overcome.

When do ionic substances conduct electricity?

They do not conduct as solids, but they conduct when molten or dissolved in water because the ions are mobile.

Charge on ions in common groups: Group 1, Group 2, Group 6, Group 7.

Group 1 form 1+; Group 2 form 2+; Group 6 form 2−; Group 7 form 1−.

What does the formula NaCl tell you about the lattice?

It shows a 1:1 ratio of Na+ to Cl− ions in the lattice.

What does a dot-and-cross diagram show in ionic lattices?

The outer-shell electrons transferred between ions; it shows ions but there are no covalent bonds between ions.

What are molecular substances made of?

Molecules joined together by covalent bonds.

Key properties of molecular substances.

Low melting and boiling points due to weak intermolecular forces; do not conduct electricity as they are neutral.

What is the difference between molecular and empirical formulas?

Molecular formula shows the exact number of atoms in a molecule; empirical formula shows the simplest whole-number ratio of atoms.

Give an example of a molecular and its formula versus its empirical formula.

Butane: molecular formula C4H10; empirical formula C2H5.

What is a polymer?

A long-chain molecule made from many repeating units; polymers can be thermosoftening.

What are giant covalent substances?

Substances with covalent bonds forming a continuous network (not discrete molecules), e.g., diamond, graphite, Si, SiO2.

Why do giant covalent substances have high melting points?

Many strong covalent bonds must be broken, requiring a lot of energy.

Why does graphite conduct electricity but diamond does not?

Graphite has delocalised electrons that move between layers; diamond has no delocalised electrons.

What is metallic bonding?

The attraction between positively charged metal ions and a 'sea' of delocalised electrons.

Why are metals good conductors of electricity?

Delocalised electrons can move freely and carry charge through the structure.

What is an alloy?

A mixture of a metal with small amounts of other elements (often other metals) to improve properties.

Why are alloys typically harder than pure metals?

Different-sized atoms distort layers and hinder sliding, increasing hardness.

What is nanoscience?

The study of nanoparticles, typically 1–100 nm, containing a few hundred atoms.

Two uses of nanoparticles (examples).

Catalysts in fuel cells (Pt nanoparticles), UV-absorbing in sun creams (TiO2, ZnO), drug delivery, cosmetics, electronics.

What are fullerenes?

Carbon molecules like C60 with hollow spherical or tube-like structures used in drug delivery, lubricants, and catalysts.

What are carbon nanotubes?

Cylindrical fullerenes with high length-to-diameter ratio; very strong and good conductors.

What is graphene?

A single layer of graphite, one atom thick; extremely strong, semi-transparent, and conducts heat and electricity.

Compare diamond and graphite (in terms of carbon bonding).

Both are giant covalent; diamond: each C forms four covalent bonds; graphite: each C forms three covalent bonds in layers with delocalised electrons.

Why is silicon dioxide (SiO2) a solid with a high melting point while CO2 is a gas?

SiO2 forms a giant covalent network with many strong bonds; CO2 is a simple molecule with weaker intermolecular forces.

What are delocalised electrons?

Electrons not bound to a single atom; free to move through the structure, enabling electrical conductivity (in metals and graphite).

What are intermolecular forces?

Weak forces between molecules that influence melting/boiling points of molecular substances.

What is monatomic structure?

A structure where particles are individual atoms (as in the noble gases) rather than molecules.

What is graphene’s significance?

A one-atom-thick layer of graphite; extremely strong, conductive, and semi-transparent with potential electronics applications.

What is a fullerene?

A hollow carbon molecule such as C60 (buckminsterfullerene) with uses in delivery, lubrication, and catalysis.

What is the effect of increasing surface area to volume in nanoparticles?

Higher surface area to volume ratio leads to different (often enhanced) reactivity and properties.

Give two examples of industries using nanoparticles and why.

Fuel cells (catalysts and cheaper Pt use); cosmetics and sun creams (UV absorption and appearance); electronics (smaller components).