Periodic Table Trends & Definitions

How to read the Periodic Table 6 C Carbon Atomic Number Elemental Symbol Elemental Name Atomic Mass

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

Chemical Reactivity Families Similar valence e - within a group result in similar chemical properties

Periodic Trends are Influenced by: Energy Level Higher energy levels are further from the nucleus Charge on Nucleus (# of protons) More charge pulls the electrons in closer + and – attract each other more Shielding Effect Blocking effect

Periodic Trends Atomic Radius size of atom: half the distance between two nuclei of a diatomic molecule Increases to the LEFT and DOWN

Atomic Radius 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 nuclear charge without additional shielding pulls e - in tighter

Periodic Trends First Ionization Energy Energy required to remove one e- from a neutral atom. Increases going UP and to the RIGHT

Periodic Trends Melting/Boiling Point Highest in the middle of a period.

Periodic Trends Electronegativity Tendency of an atom to attract electrons when chemically combined

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

Ion Group trends Each step down a group is adding an energy level Ions therefore get bigger as you go down, because of the additional energy level. Li 1+ Na 1+ K 1+ Rb 1+ Cs 1+

Ion Period Trends Across the period from left to right, the nuclear charge increases - so they get smaller. Notice the energy level changes between anions and cations. Li 1+ Be 2+ B 3+ C 4+ N 3- O 2- F 1-

Size of Isoelectronic ions Iso- means “the same” Isoelectronic ions have the same # of electrons Al 3+ Mg 2+ Na 1+ Ne F 1- O 2- and N 3- all have 10 electrons all have the same configuration: 1s 2 2s 2 2p 6 (which is the noble gas: neon)

Size of Isoelectronic ions? Positive ions that have more protons would be smaller (more protons would pull the same # of electrons in closer) Al 3+ Mg 2+ Na 1+ Ne F 1- O 2- N