1. The Periodic Table & Formation of Ions

2. Development of the Periodic Table
Mendeleev:
Considered to be the father of the periodic table
Arranged elements by increasing atomic mass
Placed elements with similar properties in columns
Left blank spaces for undiscovered elements
Was able to accurately predict properties of the undiscovered elements

3. The Modern Periodic Table
Moseley
Arranged elements by increasing atomic number
Gave a clearer pattern of periodic properties
Periodic Law: there is a periodic repetition of chemical and physical properties of elements when they are arranged by increasing atomic number

4. Arrangement of the table
Groups/Families
Columns of elements
Numbered 1 to 18
Elements have similar properties
Elements have the same # of valence electrons
Periods
Rows of elements
Numbered 1 to 7
Corresponds to number of energy levels of an atom

5. Groups with Special Names
Alkali Metals
Group 2:
Alkaline Earth Metals
Groups 3 -12:
Transition Metals
Group 17
Halogens
Group 18
Noble Gases

6. Each group contains elements with the same number of valence electrons1 2
3-12
varies 13 3 14 4 15 5 16 6 17 7 18 8

7. Example 1
Without drawing electron configurations, determine the number of valence electrons for each of the following:
A. Calcium
B. Neon
C. Sodium
D. Aluminum
E. Sulfur

8. Periodic Trends Valence electrons Atomic Radius
Ionization Energy: Energy required to remove an electron from a neutral atom
Electronegativity: The attraction of an atom for shared electrons in a covalent bond

9. Atomic Radius Increases from top to bottom in a group
Decreases from left to right across a period

11. Example 2
Arrange each of the following in order of increasing atomic radius (smallest  largest)
A. Calcium, Magnesium, Barium
B. Fluorine, Iodine, Chlorine
C. Calcium, Arsenic, Bromine
D. Chlorine, Fluorine, Oxygen

12. Ionization Energy Increases from left to right across a period
Decreases from top to bottom in a group

14. Example 3
Place the following in order of increasing ionization energy (lowest  highest)
A. Sulfur, Oxygen, Selenium
B. Calcium, Magnesium, Beryllium
C. Lithium, Fluorine, Nitrogen
D. Carbon, Silicon, Nitrogen

15. Electronegatvity Increases from left to right across a period
Decreases from top to bottom in a group

17. Example 4 Determine the most electronegative element in each pair
A. Calcium, sulfur
B. sulfur, chlorine
C. potassium, bromine
D. Silicon, phosphorus

18. Octet Rule
Typically, elements want to have 8 valence electrons (except hydrogen and helium) in order to be stable
Noble gases are stable because they have 8 valence electrons
Other elements will lose, gain, or share electrons in order to have 8 valence

19. Becoming Stable
Remember atoms are neutral because they have equal #’s of protons and electrons
When an atom gains or loses electrons, this equality is upset…
The atom is no longer neutral…and is no longer called an atom

20. Ions
An ion is an atom that has an electric charge because it has lost or gained electrons
If an atom loses electrons, its charge will become positive. It is called a cation.
If an atom gains electrons, its charge will become negative. It is called an anion.

21. On the Periodic Table Group Charge of Ion 1 + 1 2 + 2 3 -12 Varies 13
+ 3 14 15
- 3 16
- 2 17
- 1 18
Do not form ions

22. Ionic Charges
The number of electrons that an atom will gain or lose in order to become stable determines its ionic charge
Metals lose electrons and have + charge (These are called cations)
Nonmetals gain electrons and have – charge (These are called anions)

23. Size of Ions Cations (+ charges) are smaller than their parent atoms
Anions (- charges) are larger than their parent atoms

24. Example 5
Determine the ionic charge for each of the following. Indicate if it is a cation or an anion:
A. Magnesium
B. Chlorine
C. Oxygen
D. Sodium
E. Nitrogen

25. Naming Ions
If the ion is positive…name it the atom’s name followed by the word ion
Example: Sodium is Na1+…its name is Sodium ion
If the ion is negative…change the atom’s name to have an –ide ending then write the word ion
Example: Chlorine is Cl1-…its name is chloride ion

26. Example 6
Indicate the ionic charge and the name of the ion formed from each of the following elements:
A. Potassium
B. Bromine
C. Aluminum
D. Cesium
E. Fluorine

27. Element Mg F O K Na Al
# Valence electrons
Ionic Charge
Symbol
Name of ion
# of protons
# of electrons