One of the most important unifying principles of Chemistry
Patterns that develop in the elements
A table showing the elements and related information about them
Each box in the periodic table represents one element▪ It contains▪Atomic Number▪Symbol▪Average Atomic Mass
Arranged in columns called groups or families , they are organized by the number of outer energy level/ valence electrons.
18 vertical columns divided into 8-9 Groups or Families
The number of valence electrons or the reactivity level determine which group an element belongs to (In most cases the singles digit in each
group number indicates the number of valence electrons)
A horizontal row of elements in The Periodic Table. In most families, the reactivity of the
elements in the same family increases as the period increases or moves down the chart.
The smallest part of a compound, or element.
A molecule must contain two or more atoms from the Periodic Table of Elements. ▪CO2 = Carbon Dioxide▪CO = Carbon Monoxide▪Au2 = Gold
The atoms on the periodic table are called elements.
There are more than 110 known elements. ▪No element with an atomic number
greater than 92 is found naturally in measurable quantities on earth
Element can also refer to a pure molecule.
That is when a molecule has only 1 element in its composition▪O2 = Oxygen
▪Au2 = Gold
When two or more different elements combine (bond) they form a compound
Examples
▪H2O = Water
▪C6H12O6 = Glucose
▪CO2 = Carbon Dioxide
Two classifications of compounds▪Organic▪ Inorganic
A compound that contains a combination of Hydrogen (H), Carbon (C) and Oxygen (O)and derived from a living thing
Example▪ Glucose C6H12O6
A compound that does not contain Carbon.
If it does the carbon has not come from a previously living thing
Examples▪ Carbon Monoxide (CO)▪ Carbon Dioxide (CO2)
▪ Carbonates (CaCO)
The largest section located on the left side of the “stair-step line” of periodic table.
These elements are ▪Shiny▪Malleable▪Ductile▪Conductive▪High melting point (temperature)
Located to the right of the “stair-step line” on the table.
These elements are:▪Non-conductive▪No luster or not shiny, but dull
Found along the stair-step line between the metals and nonmetals.
A lot like metals but not exactly
Metalloids▪Have qualities of metals and
nonmetals▪Brittle , non-ductile and non-
malleable
Hydrogen & Helium Hydrogen▪Classified as part of Group 1 only
because it has only 1 valence electron.▪However it has its own unique set of
properties that set it apart from the other members of the group
Helium▪Classified as part of Group 8 mainly
because it has no reactivity like all of the elements in group 8. ▪Helium has only 2 valence electrons
rather that the 8 all the other members of this group do.
Dimitri MendaleevThe “Father of the Periodic Table”,
He collected all the information available in the nineteenth century about the elements
Arranged the elements by increasing atomic mass and found a repeating pattern in the physical and chemical properties
Eventually the table was rearranged by atomic number as it was more accurate that way