APchem periodicity trends

effective nuclear charge

net positive charge pulling electrons towards the nucleus

atomic radius

size of the atom

ionic radius

size of an ion

as you move across the periodic table, atomic radius decreases because…

the effective nuclear charge increases

as you move down the periodic table the atomic radius increases because…

the electrons are added to the higher energy levels

cations (+ charge) are smaller than their neutral atoms because…

the valence electrons are lost (one less energy level occupied)

anions (- charge) are larger than their neutral atoms because…

added electrons without added protons so there are more electron-electron repulsions

ionization energy

energy needed to remove an electron from an atom

as you move across the periodic table, ionization increases because…

increased nuclear charge creates stronger pull of electrons towards nucleus

as you move down the periodic table, ionizations decreases because…

electrons are farther away from the nucleus

electronegativity

an atoms ability to attract and hold electrons

as you move across the periodic table electron affinity increases because…

increased effective nuclear charge creates greater ability to attract electrons

as you move down the periodic table, electron affinity decreases because…

decreases effective nuclear charge and electrons added farther from nucleus

metallic character

reactivity determined by metals ability to give up electrons

as you move across the periodic table the reactivity of metals decreases because…

greater effective nuclear charge means electrons are closer to nucleus and harder to remove

as you move down the periodic table, the reactivity of metals increases because…

electrons are easier to remove when they are farther away from nucleus

reactivity of non-metals

reactivity determined by non-metals ability to add electrons

as you move across the periodic table the reactivity of non-metals increases because…

greater effective nuclear charge makes it easier to attract electrons

as you move down the periodic table, the reactivity of non-metals decreases because…

the number of energy levels increases which decreases the attraction of electrons to nucleus