1. A Guided Tour of the Periodic Table

2. Organization of the Periodic Table
The elements in the periodic table are organized because of the PERIODIC LAW
This states that when elements are arranged similarities in their PROPERTIES will occur in a regular pattern.

3. The PT helps determine e- arrangement
Periods
Groups
Periods on the periodic table run horizontally, left to right.
The period #s correspond to energy levels and # of orbitals that may exist there.
Groups on the periodic table run vertically, up and down.
The group #s correspond to # of valence electrons and ion charges.

4. How do structures of atoms Differ?
Protons = the atomic # of an element
Protons give the element it’s identity
Protons are given the identity Z number
Identify each element
Z=2, Z=45, Z=23
Isotopes are atoms of an element with the same # of protons, but different # of neutrons.
The Mass number is the number of protons + the number of neutrons.
Mass # is given the identity A number

5. How Do the Structures of Atoms Differ? continued
Section 2 A Guided Tour of the Periodic Table
Chapter 4
How Do the Structures of Atoms Differ? continued
Because the mass of a single atom is so tiny, atomic masses are usually expressed in atomic mass units.
An atomic mass unit (amu) is equal to one twelfth of the mass of a carbon-12 atom.
The average atomic mass for an element is a weighted average of the masses of all naturally-occurring isotopes of an element.