Periodic Trends

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

Trends z Atomic Radius z Ionization Energy z Electronegativity z Valence Electrons z Energy Levels zReactivity of Metals zReactivity of Nonmetals z Melting and Boiling Points

zAtomic Radius – Size of an atom Atomic Radius Li Ar Ne K Na

Periodic Trend: Atomic Radius Atomic Radius: Increases Atomic Radius: Decreases

z Smaller (Decreases) to the right yIncreased nuclear charge without additional shielding pulls e - in tighter z Larger (increases) going down y Jump in size of nucleus and new energy level yShielding - core e - block the attraction between the nucleus and the valence e - Atomic Radius

z Ionization Energy – Energy required to remove the outermost electrons Ionization Energy K Na Li Ar Ne He

z Increases to the right yIn small atoms, e - are close to the nucleus where the attraction is stronger and nuclear charge increases so attraction between nucleus and electrons increases. z Decreases going down yMore energy levels have electrons further from the nucleus so attraction less and the shielding affect. Ionization Energy

Electronegativity z Electronegativity – An atom’s desire to grab another atom’s electrons. Ne ArHe F Cl Li Na K

Electronegativity zIncreases to the Right yElectrons are closer to the nucleus and nuclear charge is greater so attraction between nucleus and valence electrons greater. z Decreases going down yShielding affect where electrons in lower energy levels shield the positive charge of the nucleus to the electrons so attraction is less between nucleus and valence electrons

Chemical Reactivity zFamilies ySimilar valence e - within a group result in similar chemical properties

Reactivity of Metals Reactivity of Metals: Decreases Reactivity of Metals : In creases Francium is the most reactive metal Francium most reactive Metal

Reactivity of Metals z Decreases to the right y Nuclear charge increases and electrons are closer so stronger attraction for electrons and higher ionization energy. z Increases going down y More energy levels so electrons are farther away and shielding electrons cause attraction to be less between nucleus and electrons.

Reactivity of Nonmetals Reactivity of Nonmetals: Increases Reactivity of Nonmetals : De creases Fluorine is the most reactive Nonmetal Fluorine is most reactive Nonmetal

Reactivity of Nonmetals z Increases to the right y Nuclear charge increases so stronger attraction for electrons and higher electronegativity. z Decreases going down y Nuclear charge decreases due to shielding electrons and the electrons are further away. This causes lower electronegativities.

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