1. Unit 4
Read Chapter 5
The Periodic Table

2. There are 4 elements which make up 96% of all living matter
Carbon
Hydrogen
Oxygen
Nitrogen

3. Placement of elements on the table reveals the link between the atomic structure of elements and their properties
Periodic Law: the pattern of repeating properties shown from row to row in the table

4. Dmitri Mendeleev – Russian chemist and teacher
1860’s – There were only 63 known elements at the time

5. Columns were organized by properties
Within the column, masses increased from the top to the bottom
He left spaces in the table for undiscovered elements
Video Clip

6. In the modern periodic table elements are arranged by increasing atomic number (# of protons)

7. There are 4 pieces of information for each element:
1. Name of element
2. Symbol of element
3. Atomic Number – Equals the number of protons
Atomic Mass – recorded in amu’s which is
1/12th the mass of a carbon-12 atom

8. Atomic mass – a weighted average which depends on the distribution of an element’s isotopes in nature and the masses of those isotopes
Example: Silver
51.86% of Silver atoms in nature are Silver-107
48.14% of Silver atoms in nature are Silver-109
107 x =
109 x =
Average atomic mass of silver is

9. A horizontal row is known as a Period
The number of elements in each period varies because the number of available orbitals varies

10. Each column is called a Group
Elements within a group have similar properties due to similar electron configurations

11. There are 3 different ways to classify elements on the Periodic Table
Solids, liquids, and gases (State of matter is shown
at room temperature)
Those which occur naturally and those that do not
occur naturally (Unnatural element symbols are shown in white)
Metals (left), nonmetals (right), and metalloids
(between)

13. Metals Good conductors of electric current and heat
All are solid at room temperature except for Mercury
Most are malleable and many are ductile
A majority of the periodic table are classified as metals

14. Chromium
Sodium

15. Nonmetals Poor conductors of electric current and heat
Have low boiling points
Many are gases at room temperature
Those solid at room temperature are brittle
Most reactive nonmetal is Fluorine

17. Metalloids
Have properties that fall between those of metals and nonmetals
Their ability to conduct electric current varies with temperature
Silicon is considered a semiconductor

18. Silicon Silicon and germanium are good insulators at low temperatures
and good conductors at high temperatures
Silicon

19. Most reactive metals are on the far left – Group 1
Across a period from left to right, the elements become less metallic and more nonmetallic in their properties
Most reactive metals are on the far left – Group 1
Most reactive nonmetals are on the right – Group 17
Metals in Groups 3-12 are known as Transition Metals