periodic trends. definition: half of the distance between nuclei in covalently bonded diatomic...
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Periodic Trends
Definition: Half of the distance between nuclei in covalently bonded diatomic molecule Radius decreases across a period Increased effective nuclear charge due to decreased shielding
Radius increases down a group Each row on the periodic table adds a “shell” or energy level to the atom
Atomic Radius
Table of Atomic
Radii
Period Trend:Atomic Radius
Increases for successive electrons taken from the same atom
Tends to increase across a period
Electrons in the same quantum level do not shield as effectively as electrons in inner levels
Irregularities at half filled and filled sublevels due to extra repulsion of electrons paired in orbitals, making them easier to remove
Tends to decrease down a group Outer electrons are farther from the
nucleus and easier to remove
Ionization Energy
Definition: the energy required to remove an electron from an atom
Ionization Energy: the energy required to remove an electron from an atom
Increases for successive electrons taken from the same atom
Tends to increase across a periodElectrons in the same quantum level do not shield as effectively as electrons in inner levels Irregularities at half filled and filled sublevels due to extra repulsion of electrons paired in orbitals, making them easier to remove
Tends to decrease down a group
Outer electrons are farther from the nucleus
Table of 1st Ionization Energies
Periodic Trend:Ionization
Energy
Affinity tends to increase across a period
Affinity tends to decrease as you go down in a period
Electrons farther from the nucleus experience less nuclear attraction Some irregularities due to repulsive forces in the relatively small p orbitals
Electron Affinity
Definition - the energy change associated with the addition of an electron
Periodic Trend:Electron Affinity
Electronegativity
Definition: A measure of the ability of an atom in a chemical compound to attract electrons
o Electronegativity tends to increase across a periodo As radius decreases, electrons get closer to the bonding atom’s nucleus
o Electronegativity tends to decrease down a group or remain the sameo As radius increases, electrons are farther from the bonding atom’s nucleus
Periodic Table of Electronegativities
Periodic Trend:Electronegativi
ty
Summary of Periodic Trends
Ionic Radii
Cations
Positively charged ions formed when
an atom of a metal loses one or more electrons Smaller than the corresponding
atom
Anions
Negatively charged ions formed
when nonmetallic atoms gain one or more electrons Larger than the corresponding
atom
Table of Ion Sizes