The Periodic TablePeriodic Properties

Atomic SizeAtomic size: the radius of an atom (distance

from nucleus to electron cloud) is considered. Measured in angstroms (A) : 1 cm = 1x108 A

•Periodic Trend: Atomic size within a group increases and decreases as atomic number increases. Atomic size increases

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Ionic SizeSome elements tend to gain or lose electrons

to form ions.Metals lose electrons and form positive ions

called cations.Nonmetals gain electrons and form negative

ions called anions.

Fe2+

Iron has a 2+ charge because it lost 2 electons.

Ionic SizePeriodic Trend:

Cations are smaller than original atom. Losing electrons means the nucleus has a greater attraction for electrons remaining.

Anions are bigger than original atom. Gaining electrons means the nucleus has less attraction for a greater number of electrons.

Learning CheckFor each of the following sets of atoms and

ions, decide which is the smallest.a.  Na, Na+

b.  Cl, Cl-

c.  Na+, Cl-

d.  H+, H, H-

e.  Fe2+, Fe3+

f.  F-, Ne, Na+

Learning CheckFor each of the following sets of atoms and

ions, decide which is the smallest.a.  Na, Na+

b.  Cl, Cl-

c.  Na+, Cl-

d.  H+, H, H-

e.  Fe2+, Fe3+

f.  F-, Ne, Na+

ClassworkTextbook p 255 #1,2

p 257 # 3,4 p 266 # 19

Ionization energyEnergy required to remove an electron from

an atom.Measured when element is in gaseous state.

First ionization energy: energy required to remove first electron from the highest occupied energy level.

Measured in kJ/molSome elements have second, third…

ionization energy, meaning they can lose more than one electron forming positive ions.

Trends in ionization energyIonization energy increases

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Trends in ionization energy

Ionization energy increases

Ionization energy increases within a period.As the number of protons increases, the nuclear force increases making harder to remove an electron.

Ionization energy decreases within a group.As the size of the atom increases, nuclear force has a smaller effect on electrons on highest energy level.

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ElectronegativityIs the ability of an element to attract

electrons when the atom is in a compound.Noble gases are omitted because they don’t

form many compounds.Most electronegative element is FluorineLeast electronegative element is cesium

Trends in electronegativityElectronegativity increases

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