The Atom - Atoms react or not depending on its electron structure.

- All atoms desire to have a full outer electron shell.

- Metals will lose e- and nonmetals will gain e-.

- Ions combine to form compounds.

- Like charges repel, same attract.

- When elements combine in a chemical reaction to form a new compound ~ all have filled outer electron shells.

Sodium atom (Na) Chlorine atom (Cl)

Sodium ion (Na+) Chlorine ion (Cl-)

+ -

Sodium ChlorideNaCl

(ionic bond)

CLASSIFYING MATTER

KEY WORDS

Pure Mixture CompoundMolecule Heterogeneous HomogeneousDiatomic Chemical formula Subscript

• Describe the difference between element and compound, and atom and molecule.

• Understand the various descriptions of matter.

• Understand the information in a chemical formula.

Matter: Anything that has mass and takes up space, or

volume.

Pure substanceThe particles that make up a substance are all the same kind.

Mixture Substance contains more than one kind of particle.

ElementsThe simplest form of a material; an atom is the smallest particle of an element.

CompoundsThe simplest form of any material containing two or more elements chemically bonded together.

A molecule is the smallest particle of a compound.

Element:Silver– all atoms are pure silver.

Possible to have a molecule of the same atoms:

Oxygen gas – O2 Hydrogen gas – H2

Molecules like this are diatomic – “two atoms.”

Compound:Salt – all molecules are pure sodium chloride.

Heterogeneous mixture· Particles are not evenly distributed.· Individual particles can be found.

Sand and waterPizza

Homogeneous mixture· Particles of are evenly distributed – “solution”· Cannot easily separate different parts.

Salt and waterCoke

• All matter is either pure or a mixture.

• Pure matter - elements (atoms) or compounds (molecules).

• Mixtures - homogenous (joined) or heterogeneous (separate).

• Homogenous mixtures are called “solutions”