 When elements are arranged in order of increasing atomic #, elements with similar properties appear at regular intervals.

B.Coulomb’s Law Coulomb’s Law lets us calculate the FORCE between two ELECTRIC CHARGES.

 An electron is attracted to the nucleus because of the positively charged center.  The closer the electron is to the nucleus, the more positive charge it feels.  The Shielding Principle- electrons on the interior “full” orbitals shield the outer electrons from the nucleus. They hide the positive charge from the outer electrons

 As you add protons, you add positive charge. If you increase the positive charge, you increase the force  You also increase the distance which reduces the force

 1. Effective Nuclear charge justifies trends across a period  2. Increased distance justifies trends down a group

 Atomic Radius size of atom © 1998 LOGAL

 Atomic Radius Li Ar Ne K Na

 Atomic Radius yIncreases to the LEFT and DOWN

 Why larger going down? Higher energy levels have larger orbitals Shielding - core e - block the attraction between the nucleus and the valence e -  Why smaller to the right? Increased effective nuclear charge without additional shielding pulls e - in tighter

z First Ionization Energy Energy required to remove one e - from a neutral atom. © 1998 LOGAL

 First Ionization Energy K Na Li Ar Ne He

 First Ionization Energy yIncreases UP and to the RIGHT

 Why opposite of atomic radius? In small atoms, e - are close to the nucleus where the attraction is stronger  Why small jumps within each group? Stable e - configurations don’t want to lose e -

 Successive Ionization Energies yMg1st I.E.736 kJ 2nd I.E.1,445 kJ Core e - 3rd I.E.7,730 kJ yLarge jump in I.E. occurs when a CORE e - is removed.

yAl1st I.E.577 kJ 2nd I.E.1,815 kJ 3rd I.E.2,740 kJ Core e - 4th I.E.11,600 kJ  Successive Ionization Energies yLarge jump in I.E. occurs when a CORE e - is removed.

 Melting/Boiling Point yHighest in the middle of a period.

 Ionic Radius yCations (+) xlose e - xsmaller © 2002 Prentice-Hall, Inc. yAnions (–) xgain e - xlarger

Attraction an atom has for a shared pair of electrons. higher e - neg atom   - lower e - neg atom   +

Increases up and to the right.

 Which atom has the larger radius? yBeorBa yCaorBr Ba Ca

 Which atom has the higher 1st I.E.? yNorBi yBaorNe N Ne

 Which atom has the higher melting/boiling point? yLiorC yCrorKr C Cr

 Which particle has the larger radius? ySorS 2- yAlorAl 3+ S 2- Al