1. Elements & The Periodic Table

2. Forces within an atom… 1) Electromagnetic force
Opposite charges attract
protons (+) attract electrons (-)
Like charges repel
protons (+) repel protons (+)
electrons (-) repel electrons (-)
This holds the electrons in their energy levels

3. Forces within an atom… 2) Strong force
Cancels out the electromagnetic force
Holds the protons together along with the neutrons in the nucleus
The attraction between the particles that make up the protons and neutrons (quarks) are stronger than the force of repulsion
(like 2 body builders playing tug of war)
Only works when the particles are close enough together
The neutrons help to separate the protons from each other so that they do not feel as strong of a repulsive electromagnetic force

4. Periodic Table The Periodic Table was “invented” by
Dmitri Mendeleev around 1870
At the time there were only about 65 elements discovered
Multiple chemists had determined the properties of these elements (i.e. relative masses, chemical activity, physical properties) but there was no systematic way of organizing the elements

5. Periodic Law
Mendeleev noticed that certain groups of elements had similar properties
He found that when he listed the elements in order of increasing relative mass those similar properties reoccurred in a pattern
Periodic Law:
When elements are arranged in order of increasing relative mass, certain sets of properties recur periodically

6. The First Periodic Table
Mendeleev organized elements in a table
Mass increased from left to right
Elements with similar properties in same vertical columns
He was able to predict properties of elements that had not been discovered yet

7. The Modern Periodic Table
Elements are listed in order of increasing atomic number (not relative mass like Mendeleev’s)
Elements are still grouped according to common properties

8. Location of Metals, Non-Metals, Metalloids
The Periodic Table is split by the “stair-step” line
On your Periodic Table:
Draw in the stair-step line

9. Location of Metals, Non-Metals, Metalloids, & Transition Elements
Metals are located on the LEFT of the stair-step line
Non-Metals are located on the RIGHT of the stair-step line
Metalloids are located next to the stair-step line (B, Si, Ge, As, Sb, Te, At)
Transition Elements are located in the SHORT columns
On your Periodic Table:
Write in Metals, Transition Elements, Metalloids, and Non-Metals on the top next to each section

10. Properties of Metals Physical Properties Chemical Properties
Have luster (shininess)
Conduct heat and electricity
Ductile (can be made into wires)
Malleable (can be hammered into sheets)
Chemical Properties
Tend to be electron donors (lose electrons)
Many corrode (react with water or air)
Precious metals (gold and silver) are not very reactive

11. Properties of Non-Metals
Physical Properties
Generally the opposite of metals
May be solid, liquid or gas at room temperature
Have much lower densities and melting points than metals
Chemical Properties
Tend to be electron acceptors (gain electrons)
Noble Gases (Group 18) do not react with other elements

12. Properties of Metalloids
Metalloids have properties of both metals and non-metals

13. Properties of Transition Elements
Transition elements are located in the short columns (#3-12)
Properties are more difficult to predict
Number of valence electrons can vary because the electrons shift or “transition” from one energy level to the other

14. Properties of Rare Earth Elements
Rare Earth Elements are the 2 “removed” rows (on the bottom of your Periodic Table)
These rows fit between Lanthanum (La # 57) and Hafnium (Hf #72) and Actinium (Ac#89) and Rutherfordium (Rf#104)
Many of these are man-made elements
The bottom row (#90-#103) are called the Actinoids- these are all radioactive

15. Groups on the Periodic Table
Elements are listed in groups (families)
Groups are represented in each vertical column (up and down)

16. Patterns within a Group
1) All elements in the group have the same number of valence electrons (in the tall columns) and therefore the same charge (we’ll talk more about this during bonding)
Valence electrons are the electrons in the outermost electron energy level
On your Periodic Table:
Number each column (1-18)
*Your book numbers each tall column with an A after the number and each short column with a B after the number
*Note: The transition metals (short columns) do not necessarily follow these rules, but the elements in the tall columns do!

17. Patterns within a Group: METALS
2) Metals become MORE reactive as you move DOWN a group and the ATOMS become LARGER (top to bottom)
The larger an atom is, the further those valence electrons are from the nucleus, and the easier it is to remove those valence electrons

18. Patterns within a Group: NON-METALS
3) Non-Metals become LESS reactive as you move DOWN a group and the ATOMS become LARGER (top to bottom)
Non-metals tend to GAIN electrons when they undergo chemical changes so it becomes more difficult to gain electrons when the atom is larger because the electromagnetic force is not as strong the further you get from the nucleus

19. Main-Group Elements Elements in the tall columns (1,2, 13-18)
Group 1: Alkali metals
very reactive, especially with water!
Group 2: Alkaline Earth metals
fairly reactive, but not as much as alkali metals
Group 17: Halogens
most reactive non-metals
Group 18: Noble Gases
non-reactive (have full valence shells)
Other Main Groups:
named according to element at the top of their column

20. Periods on the Periodic Table
Elements are also listed in periods
Periods are represented in each horizontal row (left to right)

21. Patterns within a Period
1) All of the elements within the same period contain the same number of electron energy levels
2) Elements become LESS metallic as you move from left to right
3) Atom size DECREASES as you move left to right
As you move left, the electromagnetic force increases between the protons and electrons, pulling the energy levels in “tighter”
On your Periodic Table:
Number the Periods 1-7

22. Noble Gases Group- Not Reactive
More Reactive
More Reactive
Noble Gases Group- Not Reactive