Atomic Structure and Periodicity Periodic Trends

Atomic Structure and Atomic Structure and PeriodicityPeriodicity

Periodic TrendsPeriodic Trends

Ionization EnergyIonization Energy

An electron can be removed from an An electron can be removed from an atom if enough energy is absorbed (+)atom if enough energy is absorbed (+)

Ionization energyIonization energy – the energy – the energy required to remove one electron from required to remove one electron from a gaseous neutral atoma gaseous neutral atom

A (g) + energy A (g) + energy A A+ + (g) + e(g) + e--

measurements of this are made on measurements of this are made on individual atoms in gas phase to avoid individual atoms in gas phase to avoid interactions with nearby atoms interactions with nearby atoms

Ionization Energy Ionization Energy


if one electron is removed, the if one electron is removed, the positive charge binds the electrons positive charge binds the electrons more tightly so 2more tightly so 2ndnd ionization energy ionization energy must be highermust be higher

the largest jump in energy is when the largest jump in energy is when you remove a core electron instead you remove a core electron instead of valenceof valence



Across Period:Across Period: requires more requires more

energy to remove energy to remove an electron so an electron so increasesincreases

because electrons because electrons added in the same added in the same energy level do energy level do not shield not shield electrons from electrons from nuclear chargenuclear charge

Down Group:Down Group: requires less requires less

energy to remove energy to remove electron so electron so decreasesdecreases

because the because the valence electrons valence electrons are farther away are farther away from protons from protons attracting themattracting them



Electron AffinityElectron Affinity

Electron AffinityElectron Affinity – the energy change – the energy change when an electron is added to a when an electron is added to a gaseous neutral atomgaseous neutral atom exothermic (-)exothermic (-)

A + eA + e- - A A-- + energy + energy

Electron AffinityElectron Affinity Across Period:Across Period:

releases more releases more energy so number energy so number increases (gets increases (gets more negative)more negative)

because electrons because electrons added in the same added in the same energy level do energy level do not shield not shield electrons from electrons from nuclear chargenuclear charge

Down Group:Down Group: releases less releases less

energy so number energy so number decreases (gets decreases (gets less negative)less negative)

because the because the electrons being electrons being added are farther added are farther away from the away from the attracting protonsattracting protons

Electron AffinityElectron Affinity

Atomic RadiiAtomic Radii

Defined by the edge of Defined by the edge of its orbital but since the its orbital but since the edges are fuzzy, edges are fuzzy, difficult to determinedifficult to determine

Atomic RadiiAtomic Radii – half the – half the distance between the distance between the nuclei of identical nuclei of identical atoms that are bonded atoms that are bonded togethertogether

Atomic RadiiAtomic Radii Across Period:Across Period:

atoms get smalleratoms get smaller because of the because of the

increased number of increased number of protons attracting protons attracting the electronsthe electrons

the electrons added the electrons added in the same energy in the same energy level do not shield level do not shield electrons from electrons from nuclear chargenuclear charge

Down Group:Down Group: atoms get largeratoms get larger increasesincreases because the because the

energy levels energy levels being added to being added to the atomthe atom

Atomic/Ionic RadiiAtomic/Ionic Radii

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Atomic Structure and Periodicity Periodic Trends