Periodic Definitions & Trends Table of Contents Lecture/Lab/Activity Date Pg# 14. The History of Atomic Models 9/14/ Structure of the Atom 9/15/ Isotopes9/16/ Beanium Lab 9/17/10 18.Electron Probability Lab 9/20/ Electron Configuration 9/21/ Orbital Diagrams9/22/ Electron Config Practice9/23/ The Periodic Table9/24/ Periodic Def & Trends9/27/10 49 Objective: The student will label a periodic table to identify and explain periodic trends including atomic radius, electronegativity and ionization energy. Agenda: The Periodic Table– Lecture

How to read the Periodic Table 6 C Carbon Atomic Number Elemental Symbol Elemental Name Atomic Mass

Definitions Atomic Number Is the same as the number of protons in an element. If this number changes the element name must change as well. Atomic # = # of protons = # of electrons Atomic Mass Is a weighted average of all the atoms in a naturally occurring sample of an element (mass & relative abundance) 1 amu – one tweflth the mass of a carbon-12 atom

Calculating Neutrons Round the Atomic Mass Atomic Mass -Atomic Number (difference = # neutrons) 6 C Carbon Example: Atomic Mass = 12 Atomic # = 6 Difference = 6 Difference = # neutrons

Calculating Atomic Mass 3 values required: # of stable isotopes of an element The mass of each isotope The natural percent abundance of each isotope ? If Element X has 2 naturally occurring isotopes, what is its atomic mass? Mass 1 = amu and has a relative abundance of %, Mass 2 = amu and has a relative abundance of 80.09%

Periodic Law When elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals.

Chemical Reactivity Families Similar valence e - within a group result in similar chemical properties

Periodic Trends Atomic Radius size of atom Increases to the LEFT and DOWN

Atomic Radius Why larger going down? Higher energy levels have larger orbitals Shielding - core e - block the attraction between the nucleus and the valence e - Why smaller to the right? Increased nuclear charge without additional shielding pulls e - in tighter

Periodic Trends First Ionization Energy Energy required to remove one e- from a neutral atom. Increases going UP and to the RIGHT

Ionization Energy Why opposite of atomic radius? In small atoms, e - are close to the nucleus where the attraction is stronger Why small jumps within each group? Stable e - configurations don’t want to lose e -

Electronegativity The attraction an element has on a shared paired of electrons

Periodic Trends Melting/Boiling Point Highest in the middle of a period.

Ionic Radius Cations (+) lose e- smaller Anions (–) gain e- larger © 2002 Prentice-Hall, Inc.