Transcript Periodic Trends

Review
The elements of the Periodic Table are arranged by:
Periods – the number of energy levels.
Groups – the number of valence electrons.
Blocks – the orbital they are filling.
Atoms can gain or lose electrons.
Metallic atoms lose e- and form cations.
Nonmetallic atoms gain e- and form anions.
Metallicity
More Metallic
Less Metallic
Less Metallic
More Metallic
Periodic Trends
Atomic Radius
 Ionic radius
 Ionization Energy
 Electronegativity
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Atomic Radius
How big is an atom and why do we need to
know?
 Atomic radius – distance from center of atom to
its outer electrons.
Atomic radius has an affect on the chemical properties of an
atom
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Decreases going left to right in a period.
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Increases going down in a group.
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More protons increases the pull on outer electrons
More energy levels added makes the atom larger
The largest atom, therefore, is Francium.
The smallest atom is Helium
Atomic Radii in Period 2
Li
Be
B
C
N
O
F
Ne
Cl
More protons means outer electrons are pulled in closer!
Br
I
At
More energy
levels means
greater atomic
size!
Atomic Radii General Trend
Radius Decreases
Radius increases
Radius decreases
Radius Increases
Ionic Radius
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Ionic Radius – the distance from the center of an ion to
its outermost electrons
In general, ionic radius follows the same trend as atomic
radius
Cations are smaller than their atoms.
– Losing electrons from outer shell makes them
smaller
Anions are larger than their atoms.
– gaining electrons expands their outer shell
Ionization Energy
Energy – the energy required to remove 1
electron from an atom.
– Increases going left-to-right in a period
• More protons increases attraction on outer
electrons
– Decreases going down in a group
• More energy levels make outer electrons harder
to hold
Ionization
– The element with the highest
ionization energy is Helium
Electronegativity
Electronegativity (EN) – The ability of an atom to attract
electrons in a chemical bond
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Increases going left-to-right in a period
● More protons increases attraction for electrons of other
elements
Decreases going down in a group.
More energy levels will shield electrons of other elements from
the positive nucleus
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Noble gases do not naturally form chemical bonds
The element with the highest Electronegativity is Fluorine
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Review
Atomic radius and ionic radius decrease left-to-right in a period
● Ionization energy and Electronegativity increase left-to-right in a
period
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The reason for these trends left-to-right is due to increasing
number of protons,
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additional protons pull outer electrons in closer
● Atomic radius and ionic radius increase going down a group
● Ionization energy and electronegativity decrease going down a
group
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the reason for these trends top-to-bottom is due to
increasing energy levels, or layers, of electrons
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additional layers increase the atomic size, and shield the
outer electrons from the positive nucleus
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