Chemistry - Metal & Alloys, Structure, Bonding, Nano-science

Alloy vs Pure Metal Structure

Pure Metal: Neat layers that easily slide over each other (soft malleable)

Alloy: Different-sized atoms disrupt layers so they cannot slide (hard)

Sonorous vs Brittle

Sonorous: Metals making a ringing sound when struck
Brittle: Non-Metals crack/shatter under force

Group vs Period

Group: Column, number of outer shell electrons
Period: Row, number of electron shells

Ionic conductivity

Solid: Cannot conduct (Ions are locked in place)
Molten/Aqueous: Conducts electricity because ions are delocalised (free) to move and carry charge

Covalent Bond Definition

A strong bond formed when non-metals share pairs of electrons. Very stable because of electromagnetic attraction between the shared and electrons and both nuclei

Why do simple molecular substances have low melting points?

Heating only breaks the weak intermolecular forces between the molecules, not the strong covalent bonds (Larger molecules=Higher melting points)

Giant Covalent Structure

A massive solid network, atoms are linked with strong covalent bonds (e.g Diamond,Graphie,Silicon)

Diamond vs Graphite Structure

Diamond: Each Carbon forms 4 bonds in a Hard 3D lattice. Rigid
Graphite: Each Carbon forms 3 bonds in Flat layers. Slippery, lubricant

Why does Graphite conduct Electricity?

Each Carbon atom has 1 delocalised electron that is free to carry charge from moving between layers (Diamond is hard with no free electrons

Graphene

Has a single, 1-atom-thick layer of Graphite. Incredibly strong & Conducts electricity well

Fullerenes & Nanotubes

Fullerenes: Hollow cages of Carbon, Hexagonal rings, Hollow sphere
Nanotubes: Long cylinders with high tensile strength used in electrons

Nano particles & Risks

Particles 1-100 nm in size with an extreme Surface area : Volume ratio Risk: Can be breathed into lungs/pass straight through cells due to their size

Fine particles vs Coarse

Fine: 100 nm - 2500 nm
Coarse: 2500nm to 10,000k (commonly called dust)

Thermosoftening vs Thermosetting Polymers

Thermosoftening: Melt when heated because chains have no cross-llink and slide
Thermosetting: Do not melt because chains are locked by strong chemical cross-links

Composite Materials

Made of two distinct parts: matrix/binder, holding together the fibres or fragments of reinforcement

Limitations of Bonding Models

Dot-and-Cross: Fails to show 3D shape / relative atom sizes
Ball-and-Stick: Fails to show bonds as physical sticks & implies huge empty spaces
Space-Filling: Fails by hiding internal bonds & Structures

Polymer Definition

A big long-molecule made up of repeating small monomers joined by strong covalent bonds