1. Trends in the Periodic Table

2. Electron Configurations
Elements organized according to valence electrons(outer electrons).
H=1s1 Li=[He]2s1 Na=[Ne]3s1 K=[Ar]4s1
Elements in a group have similar properties because they have valence electrons in similar configurations.
Periodic Table contains s, p, d and f blocks.
Electrons filling these orbitals for elements in these groups.

3. Periodic Trends
Many properties of the elements change in a predictable way as you move through the periodic table.

4. Atomic Radius Distance from center to outermost electrons.
Radius increases going down a group.
Radius decreases going left to right.

5. Atomic Radius Why does radius increase as you move across a period?
As you move down a group, electrons are in larger principal quantum #’s and are therefore further away.
Across a period – outer electrons are in same principal quantum #.
All these should be same size but they are not.
Why? Increase # of protons in nucleus creates a stronger force of attraction for electrons.

7. Ionic Size When atoms lose electrons, they become smaller.
Li atom = 0.152nm
Li+ ion = 0.060nm
Vacates largest orbital and reduces repulsive force between remaining electrons.

8. Ionic Size When atoms gain electrons they become larger.
F atom = 0.064nm.
F- ion = 0.136nm.

9. Ionization Energy
The energy needed to remove one of an atoms electrons.
8.64x10-19 joules are required to remove 1 electron from a lithium atom.
Li(g)  Li+(g) + e-
IE = 8.64x10-19 J/atom or 521kJ/mol
Measure on atoms in the gas state

10. Ionization Energy
High ionization energy means it holds onto electrons tightly.
Two trends:
Decrease as you move down a group.
Increase as you move from left to right.
Opposite of atomic radius – electrons in smaller atoms are held more strongly by the nucleus.

12. Successive Ionization Energies
For each element there is a large increase between a certain pair of ionization energies.
Nobel gas inner cores are held more strongly than valence electrons.

13. Electron Affinity
Energy change that occurs when an atom gains an electron.
Ne(g) + e-  Ne-(g) EA = 29KJ/mol
29KJ is needed to add an electron to 1 mol of Neon.
F(g) + e-  F-(g) EA = -328KJ/mol
328KJ is released when 1 mol of F gain electrons.
Atoms with greater attractions for added electrons have more negative EA.

15. Electronegativity Ability to attract electrons in a chemical bond.