1. The Periodic Table
Physical Science Unit 8

2. Part 1:
Periodic Table

3. Early Tables Antoine Lavoisier – late 1700’s
Compiled a list of all known elements at the time and placed them into four categories
Dimitri Mendeleev – late 1800’s
Demonstrated a connection between atomic mass and elemental properties
Ordered by increasing atomic mass
Into columns with similar properties
Left blank spaces for where he thought undiscovered elements would be placed
Henry Moseley
Ordered elements based on Atomic Number (number of protons)

4. Mendeleev’s Table

5. Periodic Law
States that there is a periodic (recurring) pattern of chemical and physical properties of the elements when they are arranged by increasing atomic number (number of protons)

6. Modern Periodic Table Consists of boxes typically containing
Element name
Symbol
Atomic number
Atomic mass
Boxes arranged in order of increasing atomic number with
Series of columns called groups or families
Series of rows called periods

7. Atomic Mass
Mass of the atom is mostly a result of the protons and neutrons in the nucleus.
Electrons weigh almost nothing
Unit of measurement is called the atomic mass unit or amu
1 amu is equal to 1/12 the mass of a carbon-12 atom

8. Average Atomic Mass
The mass of an element is determined by taking the average mass of all the isotopes of that element.
It is this average mass that is used as the amu for the element on the periodic table

9. Why the Weird Shape?
Elements are not only in numerical order of protons, but also grouped by characteristics and properties of elements

10. Columns and Rows Groups – the vertical columns of the periodic table
Representative elements in group have same number of outer electrons
All elements in group have similar properties
Periods – the horizontal rows of the periodic table
Rows indicate energy level of an atom’s electrons

11. Basic Structure 7 periods beginning with hydrogen 18 groups
Representative Elements – often called the “main group” and contains groups 1,2, and 13-18
Transition Elements – (in the center) containing groups 3 to 12
Element Classification – classified as metals, non-metals or metalloids

13. Types of Elements Metals – left side Metalloids – in between
Non-metals - right side

14. Metals Characteristics – Most are malleable and ductile
1. shiny (when smooth and clean)
2. solid at room temperature
3. good conductors of heat and electricity
4. high mp and bp
Most are malleable and ductile
Most elements are metals

15. Types of Metals Alkali Metals – group 1 elements (except for hydrogen)
Very reactive
Usually exist as compounds with other elements
Alkaline Earth Metals – group 2
Transition Metals – groups 3-12
Inner Transition Metals – 2 rows at the bottom of table called the lanthanide series and the actinide series

16. Non-Metals Occupy the upper right side of the periodic table
Low melting and boiling points
Generally gases or brittle, dull-looking solids
The only liquid at room temperature is bromine

17. Groups of Non-Metals Halogens – group 17 Noble Gases - group 18
highly reactive and often found in compounds with other elements
Noble Gases - group 18
Very stable
unreactive

18. Metalloids Elements bordering the stair step line
Have chemical and physical properties of both metals and non-metals

20. Electrons and the Periodic Table
Part 2:
Electrons and the Periodic Table

21. Electrons in Atoms
Can use periodic table to determine number and position of electrons
How?
Each row tells you what energy shell or level you are in.
Energy level one has up to 2 electrons
Energy level two has up to 8 electrons
In a neutral atom, there are the same number of protons as electrons

22. Valence Electrons
Use the periodic table to determine the number of outer level electrons
Outer level electrons are called valence electrons
Group number on periodic table tells you number of valence electrons
Number of valence electrons determines the chemical behavior of an element

23. Group number –
# of valence
electrons

24. Lewis Dot Structure
Use group number to determine number of valence electrons – also called electron dot
Write chemical symbol then add dots one at a time up to 8 total Ex
Fluorine
In group 17 – so 7 valence e-
Chemical symbol – F
Dot structure F

25. Octet Rule
Most atoms are always trying through reactions to achieve a full set of 8 electrons in their outermost energy level.
Bohr model doesn’t explain this, so we will delve a little bit into the quantum mechanical model to explain why this is so.

26. Magic Number “8” Why 8? (remember energy level 3 with 18 e-?)
Energy levels don’t fill in sequential order.
The energy level have sections called orbitals
Think of it like a theater having sections and each section has rows – ex Balcony section: Row s
That is how electrons work too
These rows or orbitals are called
s, p, d, f
They are represented in blocks on the periodic table
For any element beyond He on the table, the highest energy level electrons in any one particle period will be no more than 8 explaining the octet rule
Total number of electrons in lower energy levels can achieve their regular amounts (2, 8, 18, 32)

27. Let’s Take a Closer Look
d-block electrons are always one energy level lower than the s and p in the same period.
so valence electrons are the total of s and p electrons.

28. Energy Levels and Orbitals
Only s
Energy level 2 –
s and p
Energy level 3 –
s, p, d
Energy level 4 –
s, p, d, f
nucleus

29. Actual Shapes
Actual shapes look like this around the nucleus

30. Common Ion Charges
Because of this, we can use the group numbers along with the octet rule to determine what ion an atom is likely to form for many of the representative elements
Group 1 (alkali metals) – have 1 valence e-
They want to lose this one and go down to the lower level that is full so form 1+ ions
Group 2 (alkaline earth metals) – have 2 valence e-
They want to lose these two and go down to the lower level that is full so form 2+ ions
Group 17 (halogens) – have 7 valence e-
They want to gain one more electron and
fill their outer level and so form 1- ions

32. Images http://killgerm.com/images/periodic_table.jpg