Transcript Even More About the Periodic Table

Even More About the
Periodic Table
Periodic Trends
Trends in Atomic Size
 Atomic radius - one-half the distance
between the nuclei of two atoms of the
same element when the atoms are joined
 In general, atomic size increases from top
to bottom within a group and decreases
from left to right across a period.
Trend in Ionic Size
 Cations are always smaller than the
atoms from which they form.
 Anions are always larger than the
atoms from which they form.
Trends in Ionization Energy
 First ionization energy tends to
decrease from top to bottom within
a group and increase from left to
right across a period.
Trends in Electronegativity
 In general, electronegativity values
decrease from top to bottom within
a group. For representative
elements, the values tend to
increase from left to right across a
period.
Summary of Trends
 The trends that exist among these properties
can be explained by variations in atomic
structure.
 The increase in nuclear charge within groups
and across periods explains many trends.
 Within groups an increase in shielding
(distance from the nucleus) has a significant
effect
Atomic size DECREASES
Ionization energy INCREASES
Electronegativity INCREASES
Nuclear charge INCREASES
Shielding is constant
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Atomic size INCREASES
Ionization energy DECREASES
Electronegativity DECREASES
Nuclear charge INCREASES
Shielding INCREASES
Ionic size INCREASES
1
2
Size of cations
decreases
13
14
15
16
Size of anions
decreases
17
Periodic Trends Notes
Electron Shells
 Ground State means no electrons are
where they are not supposed to be.
 Excited state is when the electrons
absorb energy and jump up to a higher
electron shell or energy level.
 When electrons fall back down to the
ground state they emit a specific
amount of energy which is noticed as a
specific color (or colors) of light.