Trends in the Periodic Table Periodicity Trends in the Periodic Table

Atomic Radius One half the distance between nuclei of identical atoms that are bonded together Decrease across a period due to increasing positive nuclear charge Increase down a group due to increasing number of energy levels (outer electrons are farther from the nucleus)

Ionization Energy Ion: An atom or group of atoms that has a positive (cation) or negative (anion) charge Ionization: The formation of an ion Ionization Energy: The energy required to remove one electron from a neutral atom of an element, measured in kilojoules/mole (kj/mol)

Ionization Energy IE increases for each successive electron Each electron removed experiences a stronger effective nuclear charge Greatest increase in IE comes when trying to remove an electron from a stable, noble gas configuration.

Ionization Energy IE tends to increase across each period. Atoms are getting smaller, electrons are closer to the nucleus IE tends to decrease down a group Atoms are getting larger, electrons are farther from the nucleus Outer electrons becomes increasingly more shielded from the nucleus by inner electrons Metals have characteristically low IE Nonmentals have high IE Noble gases have a very high IE

Ionic Radius Cations have a smaller ionic radius than corresponding atom Protons outnumber electrons Less shielding of electrons Anions have a larger ionic radius than corresponding atom Electrons outnumber protons Greater electron-electron repulsion Ion size decreases down a group

Electron Affinity Energy change that occurs when an atom accepts an electron Halogens have the highest electron affinities Metals have low electron affinities Affinity tends to increase across a period and decrease down a group

Electronegativity The ability of an atom to attract electrons when bonded Nonmetals have high electronegativity Metals have low electronegativity Electronegativity increases across a period and decreases down a group

Electronegativity Electronegativity