Suggested Reading Pages 150 - 164 Section 5-3 Periodic Trends Suggested Reading Pages 150 - 164 Section 5-3

Valence Electrons Electrons available to be lost, gained, or shared in the formation of chemical compounds Outer energy level

Atomic Radius Distance from the center of atom’s nucleus to outermost electron.

Atomic Radius Decreases UP and to the RIGHT Or Increases DOWN and to the LEFT

Atomic Radius K Na Li Ar Ne

Atomic Radius Describe in terms of atomic structure: Going down a group from top to bottom, adding energy levels. Higher energy levels have larger orbital's Describe in terms of atomic forces: Shielding Effect ~ inner core e- block the attraction between the nucleus and the valence e-

Atomic Radius Describe in terms of atomic structure: Electrons remain in the same energy level (not farther away) Describe in terms of atomic forces: Increased nuclear charge (+) without additional shielding pulls e- in tighter

Ion An atom or group of bonded atoms that has a positive or negative charge.

Ionic Radius Cations (+) lose e- smaller Anions (–) gain e- larger © 2002 Prentice-Hall, Inc.

Ionic Radius Larger – down a group. Smaller – across a period. Cations: Smaller than neutral atom Anions: Larger than neutral atom

Trends in Ionic Size Trends in Ionic Size 6.3 Size generally increases The ionic radii for cations and anions decrease from left to right across periods and increase from top to bottom within groups. 11

Ionization Energy The amount of energy required to remove an electron from a neutral atom. Increases UP and to the RIGHT

Ionization Energy

Ionization Energy Opposite trend from atomic radius. Larger atoms ~electrons held less strongly ~ takes less energy to remove one. Smaller atoms ~ electrons held more strongly ~ takes more energy to remove one.

Ionization Energy Why small jumps within each group? Stable electron configurations do not easily give up electrons

*1st, 2nd, and 3rd Ionization Energies Amount of energy to remove 1st electron, 2nd electron, 3rd electron. Each higher ionization requires more energy. Na  Na+ + e- 496 KJ/mol Na+  Na+2 + e- 4565 KJ/mol Na+2  Na+3 + e- 6912 KJ/mol

Electron Affinity The energy change that occurs when an electron is added to an atom.

Negative Electron Affinities Energy is given off when an electron is added to an atom. Non-Metals tend to gain electrons. Non-Metals have NEGATIVE affinities.

Positive Electron Affinities Energy is required to add an electron to an atom. Metals tend to lose electrons Metals have POSITIVE affinities.

Noble Gas Electron Affinities Noble Gases have high positive electron affinities. Octet Rule! 8 valence electrons

Electronegativity The ability of an atom to attract electrons Predict using octet rule and atomic radius. F is most electronegative, Cs and Fr are least electronegative.

Electronegativity