#engineering/y11
Elements, compounds and mixtures §
Element - A chemically simple substance made up of atoms all of the same kind.
Compound - A compound is formed when two or more elements chemically combine in fixed proportions by weight.
Pure Substance - An element or compound
Mixture - is formed when two or more pure substances are mechanically mixed together in any proportion
| Metals | Non-metals |
|---|
| Usually solid at ordinary temperatures | May be solids, liquids or gases |
| Are lustrous on a freshly cut surface | Usually dull if solid |
| Usually malleable and ductile to some degree | Usually brittle if solid |
| Usually good thermal and electrical conductors | Usually non conductors (insulators) of heat and electricity |
| Usually form alloys | Do not alloy, but may chemically combine to form compounds. |
Definitions §
- Malleable: Ability of a sheet of metal to be bent
- Ductility: Ability of a metal to be drawn into wire
- Lustrous: Shiny
- Brittle: Broken easily
- Alloy: A mixture of two or more metals
Solids, Liquids, and Gases §
| Property | Solids | Liquids | Gases |
|---|
| Definite ordered arrangement | Yes | No (Random atomic arrangement) | No (Random atomic arrangement) |
| Energy Levels | Low | Higher | Very High |
| Compressibility | Practically incompressible | Compressible to an extent | Readily compressible |
| Diffusion Rate | Very slow | Faster | Extremely rapid |
| Shape & Volume | Definite shape and volume | Takes shape of container, fixed volume | Takes shape and volume of container |
| Crystallinity | True solids are crystalline | Non-crystalline | Non-crystalline |
- (Structure) → (Properties) ← (Process)
Levels of Structure: §
- Macrostructure
- Microstructure
- Atomic Structure
Atomic Structure §
Historical Models of the Atom §
| Year | Scientist(s) | Model Description |
|---|
| 1808 | Dalton (A) | Hard, visible ball |
| 1900 | Thompson (B) | Electrons embedded in a sphere of positive charge |
| 1912 | Rutherford (C) | Negative electrons orbiting a positive nucleus |
| 1932 | Bohr-Chadwick (D) | Electrons orbiting a nucleus of protons and neutrons |
The Bohr Atom §
| Shell | Sub-Orbitals |
|---|
| K - 2 | s |
| L - 8 | p |
| M - 8/18 | d |
| N - ? | ? |
Chemical Bonding §
Primary Bonding Types: §
- Ionic Bonding