I II III Periodic Trends

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.

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

Li Ar Ne K Na

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 Atomic Radius

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

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

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

Trends in Ionic Size  Trends in Ionic Size 6.3 Size generally increases

 The amount of energy required to remove an electron from a neutral atom.  Increases UP and to the RIGHT 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? Ionization Energy  Stable electron configurations do not easily give up electrons

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

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