1. Chapter 5 – Modern Chemistry
Periodic Law
Chapter 5 – Modern Chemistry

2. 5.1 History of the Periodic Table
Dmitri Mendeleev
Created with the first periodic table
Organized it according to atomic mass
Discovered that the table exhibited chemical periodicity
Repeating pattern of chemical properties
Correctly stated as periodic law

3. History of the Periodic TAble
Henry Mosley
Reorganized table according to atomic number
His work also led to the modern definition of the atomic number
Working with Ernest Rutherford

4. Modern Table Noble Gases Lanthanides Actinides
John William Strutt and Sir William Ramsey discovered argon and helium
Discovered from line emission spectrums from the sun
Led to Group 18
Lanthanides
Early 1900’s
Discovery in Ytterby
Actinides
Final piece to the table
Many man made elements

5. 5.2 Electron Configuration

6. S and P block S block P block
Groups 1 and 2
Period is the same as the principle energy level
P block
Groups 13 – 18
These two blocks make up the outer most configuration (valence shell) of the element

7. D and F Block D block F block Groups 3-12 (Transition Metals)
Electrons fall into an interior shell
Period – 1 is equal to the principle energy level
F block
Inner Transition Metals
Electrons also fall into interior shells
Period – 2 is equal to the principle energy level

8. 5.3 Periodic Trends Atomic Size (Radius)
Periods (moving left to right)
Decrease
Due to a lessening of the shielding effect
Shielding effect is a phenomena in which the interior electrons will ”shield” the pull of the nucleus from the outer most electrons
As more and more outer electrons are added to the valence shell, it becomes harder for the interior electrons to ”shield” the outer electrons
This causes the energy level to be pulled closer to the nucleus
Groups (top to bottom)
Increase
Due to increase in outer energy levels

9. Periodic Trends Ionization Energy
Ionization is the process of atoms forming ions to fulfill the octet rule
Ionization Energy is the energy associated with removing electrons
Periods
Increase (harder to remove electrons)
Result of a lessening of the shielding effect
Nucleus has a greater pull on the outer most electrons
Groups
Decrease
Further from the nucleus due to increase in energy levels

10. Periodic Trends Ionic Size (Radius)
Depends on the type of ion that is formed
Positive Ions (Groups 1, 2, and 13)
Positive Ions are formed by losing electrons
Group 1 loses 1 electron, group 2 loses 2 electrons, and group 13 loses 3 electrons
More electrons that are lost the greater the positive charge and the stronger the pull of the nucleus
Decrease in size from groups 1 to 13

11. Periodic Trends Ionic Size (Radius)
Negative ions (Groups 15, 16, and 17)
Negative ions are formed by gaining electrons
Group 15 gains 3, group 16 gains 2, and group 17 gains 1
The more electrons that are gained the further the cloud can pull away from the nucleus
Decrease in size from group 15 to 17

12. Periodic Trends Ionic Size Increases down a group
Doesn’t matter whether it is positive or negative
Increase is still a result of an increase in outer energy level
Comparing Ionic size and Atomic size
Smallest to largest across a period
Metal ion < nonmetal atom < metal atom < nonmetal ion

13. Periodic Trends Electron Affinity
Energy change associated when an atom gains an electron (negative energy value)
Can also be defined as the energy when a negative ion loses an electron (positive energy value)
Periods
Increase
Explained by the octet rule
Groups
Decrease
Increase in energy level in which size affects affinity

14. Periodic Trends Electronegativity
This is the ability of an atom when forming a covalent bond to draw the shared electrons closer to its own nucleus
Periods
Increase
Due to a lessening of the shielding effect
Groups
Decrease
Due to the outer most electrons getting further from the nucleus

15. Periodic Trends Valence Electrons Group 1 – 1 valence