CHAPTER 6 THE PERIODIC TABLE

HISTORY Antoine Lavoisier Dmitri Mendeleev Increasing mass Properties Made predictions about missing elements

HISTORY Henry Mosley Used the atomic number to alter Mendeleev’s table – properties fit better as a result Periodic Law - Pattern of Repeating Properties

Elements in a group or “family” have similar properties. Periods = Energy Levels

Largest class of elements on the Periodic Table - Metals. 80% of the elements. PERIODIC TABLE: ELEMENT CLASSIFICATIONS

Groups/Families

1A 2A 3B 4B 8A 6A 7A 4A 5A 3A 6B 7B --8B--1B2B 5B Rare-Earth metals or Inner transition:

Modern periodic table – stretched out (7 rows) Shows periods with Lanthanide & Actinide series or inner transition metals where they really belong THE PERIODIC LAW

VALENCE ELECTRONS Why do the elements in a group have similar properties?

They have the same number of valence electrons. The properties are not identical because the valence electrons are in different energy levels. A valence electron is an electron that is (generally) in the highest occupied energy level of an atom. Valence electrons play a key role in chemical reactions. VALENCE ELECTRONS Why do the elements in a group have similar properties?

VALENCE ELECTRONS How do we determine the number of valence electrons?

PERIODIC TRENDS Atomic Radius Ionic Radius Ion – Charged atom or group of atoms – result of gaining or losing electrons to fulfill the Octet Rule Cation – Postive Ion – Loses electrons (metals) Anions – Negative Ion – Gains Electrons (nonmetals) Ionization Energy Electronegativity

ATOMIC RADIUS

TRENDS PG 178 Atomic Mass Increases Atomic Radius Decreases Ionization Energy Increases Electronegativity Increases Atomic Mass Increases Atomic Radius Increases Ionization Energy Decreases Electronegativity Decreases