1. Periodic Trends

2. Review - Periodic Law
When elements are arranged in order according to their atomic number, certain trends appear.
All elements in the same column have very similar properties.
All first column elements react with water.
Elements in the second column form compounds with elements in Chlorine’s column with the formula MX2

3. Review - Periodic Table
The rows on the periodic table are called either periods or series
The columns on the periodic table are called either groups or families
The elements at the top of each group are called representative elements.

4. Review of the Periodic Table Elements
Atomic Number
Atomic Mass Number
Atomic Mass
Ion
Isotope

5. Review -Valence Electrons
Outermost electrons in an atom
Examples: ….
The electrons involved in chemical bonding
They play a key role in the formation of ions
As you go from left to right across the periodic table, the number of valence electrons goes up (except for the transition metals)

6. Periodic Trends Atomic Radii Ionic Radii Ionization energy
Electronegativity
Electron affinity
Shielding

7. Atomic Radii
The radius of an atom is found from the distance between nuclei in a molecule.

8. Trends in Atomic Size
Size increases going down a column of the periodic table.
Size decreases from left to right in a row.

9. Trends in Atomic Size Cs 6s Rb 5s K 4s Na 3s Li 2s
In a family, size increases with the addition of successive electron shells.
Example: The alkali metals Cs 6s Rb 5s K 4s Na 3s Li 2s

11. Ions Ions are atoms that have either gained or lost electrons
Cations are positive ions – meaning they have lost electrons
Anions are negative ions- meaning they have gained electrons

12. Ionic Radius vs. Atomic Radius
Cations have lost electrons and become smaller than their parent atom
There are more protons per electron
The pull on the electrons is greater
The greater the pull, the smaller the size
Anions have gained electrons and become larger than their parent atom
There are less protons per electron
The pull on the electrons is less

14. Ionization Energy
It takes energy to pull electrons away from elements.
The energy required to remove the first electron from an atom is called the first ionization energy I1
The energy required to remove the second electron from an atom is called the second ionization energy I2

15. Trends in Ionization Energy
I1 decreases going down a column of the periodic table.
It is easier to pull away electrons that are farther away from the nucleus
I1 increases from left to right in a row.
It is more difficult to pull electrons away from an atom as the number of protons are increases in the nucleus

16. Trends in Ionization Energy
Arrange the following with increasing ionization energy:
C, K, Mg, Na, Ne, Si
K < Na < Mg < Si < C < Ne

19. Valence Electrons Outermost electrons in an atom Examples: ….
Often the electrons involved in chemical bonding
They play a key role in the formation of ions

20. Ions Charged Atoms Na+ has 10 e-s Ne has 10 e-s
Na+ and Ne are Isoelectronic, meaning they have the same number of electrons

21. “8 IS GREAT!!!”
Atoms are like people…. They like to be as relaxed as possible. Atoms like to exist in as low an energy state as possible
Atoms strive to lose or gain electrons to achieve a noble gas configuration….
8 electrons in the outer shell is the least energetic electron configuration, so elements will lose, or gain electrons to achieve this state

22. Predicting Ion Charges
Predict the most likely charge on the ions of: Li S Ca Cl

24. Those ODD Transition Metals
Many can form multiple ions
Ex: Fe2+, Fe3+
These elements are said to be multivalent
Fill in most likely charge states on the P.T

25. Electronegativity The electrons “desire” for its electrons
The stronger the electronegativity, the stronger an atom will cling to its electrons
Electronegativity increases as you go from left to right on the periodic table
Electronegativity increases as you go from bottom to top on the periodic table

28. Electron Affinity
Electron affinity is a measure of the energy that is given off when an atom gains an electron to become an anion
Electron affinity increases from bottom to top and from left to right on the periodic table

29. Shielding
Shielding describes the effect of inner electrons reducing the attraction of the nucleus on the outside electrons.
The more shells (energy levels), the greater the shielding effect will be.
Shielding is why larger atoms have a lower electronegativity, and smaller ionization energies. The protons don’t pull as hard