DAILY QUESTION

October 2, 2008

1. The rows on the periodic table are called _________.

2. The columns on the periodic table are called__________.

Agenda 10/2/08

• Daily Question

• Chapter 4 Section 2 Notes

Assignments: 1. No assignment tonight.

Organization of the Periodic Table (pg. 111)

• Groups similar elements together

• Elements are represented by their symbols

• Order is based on the number of protons (The Atomic Number of the atom)– Hydrogen has 1 proton, so it is first in the table

Periodic Law

• Order of periodic table is based on this

• States: when elements are arranged by the number of protons, similarities in their properties will occur in a regular pattern

Periods

• Horizontal rows in the periodic table

• Can determine the number of electrons based on the element’s location

Groups

• Columns in the periodic table

• Atoms of elements in the same group have the same number of valence electrons; therefore they have similar properties

Ions

• Atoms that have a net electric charge– Have either lost or gained electrons

• Cation = a positive ion (lost electrons)

• Anion = a negative ion (gained electrons)

Ions continued

• Having just 1 valence electron makes the atom highly reactive

• Having a full energy level makes the atom less reactive

Atomic Number

• Atomic # = # of protons of an atom

• In a “happy atom”, it also = # of electrons

• Each element has a different atomic number

• Atomic number never changes

Mass Number

• Mass number = # of protons + # of neutrons

• Elements can have a different mass #– Isotopes of an atom

Isotopes

• An atom with the original number of protons and electrons, but a different number of neutrons (Therefore a different mass number)– Example: Hydrogen Isotopes:

Protium, Deuterium, and Tritium

Calculating the # of Neutrons in an Atom

• # of neutrons = mass # – atomic #

Atomic Mass Unit (amu)

• Is equal to one-twelfth of the mass of a carbon-12 atom

Average Atomic Mass

• A weighted average of the isotopes, so the more commonly found isotopes have a greater effect on the average than rare isotopes