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 Chloride NaCl (ionic bond)

CLASSIFYING MATTER

KEY WORDS Pure Mixture Compound Molecule Heterogeneous Homogeneous Diatomic 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 substance The particles that make up a substance are all the same kind. Mixture Substance contains more than one kind of particle.

Elements The simplest form of a material; an atom is the smallest particle of an element. Compounds The 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 – O 2 Hydrogen gas – H 2 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 water Pizza

Homogeneous mixture  Particles of are evenly distributed – “solution”  Cannot easily separate different parts. Salt and water Coke

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”