2.04 Mini-Lesson: The Tiny World of Pure Substances

pure substances

Pure substances are made up of a large amount of individual atoms or molecules.

Atomic Structure

The atomic or molecular structure of pure substances varies based on:

• The types of atoms and molecules involved

• Whether or not the particles in the substance are attracted to each other

Pure Substances

Atomic Structure

1. xtended structures formed by individual atoms of the same type.

2. Extended structures formed by repeating individual atoms of different types.

3. Individual atoms that are not attracted to each other.

4. Molecules of different types of atoms that are not attracted to each other

5. Molecules of the same type of atom that are not attracted to each other

6. Molecules of different types of atoms that are attracted to each other to form extended structures

Extended structures

of individual atoms of the same type

individual atoms of the same type that are connected to form extended structures.

extended structures

Graphite is made of only carbon atoms. They are arranged in sheets. Because they are arranged in sheets, the atoms easily slide past each other. This makes graphite a soft solid that can be used in pencil lead.

example: Graphite

carbon atoms are arranged in sheets of hexagons

pure graphite

pencil lead

Diamond

it is incredibly strong. This is because of the arrangement of the atoms. The carbon atoms are bonded in a tetrahedral shape.

gold

Gold atoms are usually arranged in cubes with an atom at each corner

Repeating structures

are patterns that extend infinitely in three dimensions, characteristic of certain pure substances such as crystalline solids.

salt

repeating structure

Non-attracted Particles

that do not exert forces on each other, typically found in gases and some liquids, leading to a lack of structure. helium, neon lights

Non-attracted Molecules

molecules that do not interact significantly with one another, seen in gases and some liquids. like carbon dioxide and oxygen

attracted molecules

molecules that experience significant interactions, resulting in a structured arrangement, such as in solids and some liquids. like plant fibers and nylon