Groups of the Periodic Table

Valence Electrons  The electrons in the OUTERMOST energy level of the atom. These are the electrons furthest from the nucleus. They determine the element’s reactivity and bonding patterns.

Hydrogen & Helium  They are different from the other elements, because their TOTAL ELECTRONS are their VALENCE ELECTRONS. H has 1 total electron- it is its valence electron He has 2 total electrons- they are its valence electrons.

Alkali Metals  Located in Group I  Soft/easy to cut  HIGHLY REACTIVE (air & water)  1 valence electron (s 1 )

Alkaline Earth Metals  Located in Group II  Exhibit all properties of metals PLUS:  Two valence electrons s 2  Very reactive

Transition Metals  Located in the middle block  Shiny/good conductors  Less reactive than the other metal groups  D orbitals are filled

Halogens  Located in Group VII  Specific group of nonmetals  MOST REACTIVE NONMETALS  Seven valence electrons (s 2 p 5 )  Like to react with alkali metals and alkaline earth metals to form salts  May be solid, liquid or gaseous element

Noble Gases  Located in Group VIII  “Inert gases”- nonreactive  Eight valence electrons (s 2 p 6 )

Periodic Law  Many of the physical and chemical properties of elements repeat periodically when arranged by atomic number.

Laws  Generalizes many observations  EXPLAIN Does not address WHY

Theory  Summarizes a group of hypotheses that have been supported with repeated testing Can be changed Explains WHY

 Why is the “periodic law” considered a law and not a theory?