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I II III
Periodic Trends
The Periodic Table
0
50
100
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250
0 5 10 15 20Atomic Number
Ato
mic
Ra
diu
s (
pm
)
Periodic Law
When elements are arranged in order of
increasing atomic #, elements with similar
properties appear at regular intervals.
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50
100
150
200
250
0 5 10 15 20
Ato
mic
Ra
diu
s (
pm
)
Atomic Number
Same number of valence electrons = similar properties
Li 1s2 2s1 Na 1s2 2s2 2p6 3s1
In any group, the element BELOW has one more occupied energy level than does the element ABOVE.
The period that an element is in is the same as the energy level that its valence electrons are in.
Li in 2nd period Na in 3rd period
val. e- in 2nd val e- in 3rd
Metallicity
More Metallic Less Metallic
Mo
re M
etal
lic
Les
s M
etal
lic
Periodic Trends and Factors
There are trends in properties of elements left right AND up down trends
Trends Atomic Radius Ionic Radius Ionization Energy Electronegativity
Factors: Columbic attraction and Sheilding effect
I II III
Periodic Factors
Coulombic attraction depends on…
2– 2+
2+ 2– 1–
2–
1+
2+
amount of charge distance between charges
+ + – –
H
He
+ –
+ – + –
As we go ,
more coulombic
attraction, no new
energy level, more
pull, smaller size
shielding effect: kernel e– “shield” valence e–
from attractive force of the nucleus
Li
v.e–
K
v.e–
-- caused by kernel and valence e–
repelling each other
As we go , shielding effect increases.
tougher to
removeeasier
to remove
I II III
Atomic Radius
Atomic Radius
The size of a neutral atom Increases as we go down
Why?Add a new energy level each time (larger orbitals)
Decreases as we go across Why?
It has do to with coloumbic attraction (attraction between + and -)
Atomic Radius
Li
Na
K
Rb
Cs
ClSPSiAl
BrSeAsGeGa
ITeSbSnIn
Tl Pb Bi
Mg
Ca
Sr
Ba
Be FONCB
1.52 1.11
1.86 1.60
2.31 1.97
2.44 2.15
2.62 2.17
0.88 0.77 0.70 0.66 0.64
1.43 1.17 1.10 1.04 0.99
1.22 1.22 1.21 1.17 1.14
1.62 1.40 1.41 1.37 1.33
1.71 1.75 1.46
IA IIA IIIA IVA VA VIA VIIA
1
2
3
4
5
6
7
Decreases to the LEFT and increases DOWN
Atomic Radius
Which atom has the larger radius?
Be or Ba
Ca or Br
Ba
Ca
Examples
I II III
Ionic Radius
Ionic Radius Cations (+)
lose e-
smaller
© 2002 Prentice-Hall, Inc.
Anions (–)
gain e-
larger
Ionic Radius
Ionic Radius
As you go down, the ionic radius increases due to more energy levels.
As you go across The ionic radius of metals decreases
until middle of periodic table, slight increase, and then decrease.
Due to lose or gain of electron
Which particle has the larger radius?
S or S2-
Al or Al3+
S2-
Al
Examples
I II III
Ionization Energy
Ionization Energy
The energy required to remove an electron from an atom.
Each successive ionization requires more energy than the previous one.
As we go down, the first ionization energy decreases (due to shielding).
As we go across, the first ionization energy increases.
Successive Ionization Energies
Mg 1st I.E. 736 kJ
2nd I.E. 1,445 kJ
Core e- 3rd I.E. 7,730 kJ
Large jump in I.E. occurs when a CORE e- is removed.
Ionization Energy
Al 1st I.E. 577 kJ
2nd I.E. 1,815 kJ
3rd I.E. 2,740 kJ
Core e- 4th I.E. 11,600 kJ
Successive Ionization Energies
Large jump in I.E. occurs when a CORE e- is removed.
Ionization Energy
Which atom has the higher 1st I.E.?
N or Bi
Ba or Ne
N
Ne
Examples
I II III
Electronegativity
Electronegativity
Tendency of an atom to attract electrons in a chemical bond. Excludes noble gases.
As you go down, electronegativity decreases.
As you go across, the electronegativity increases.
Electronegativity
Why smaller going down? The higher the energy level, the less the
electron attraction of the atom.Why larger going across?
As the number of valence electrons increases, the electron attraction of the atom increases.
Electronegativity
Values Lowest values– metals at the far left
Lose electrons Highest values – nonmetals at the far
rightGain electrons
I II III
Other Periodic Trends
1
2
3
4 5
6
7
Melting/Boiling Point Highest in the middle of a period.
Melting/Boiling Point
Which atom has the higher melting/boiling point?
Li or C
Cr or Kr
C
Cr
Examples
I II III
Summary
Let’s Recap
Summary of Periodic Trends
Ionic size (cations) Ionic size (anions)
decreases decreases
Shielding is constant
Atomic radius decreases
Ionization energy increases
Electronegativity increases
Sh
ield
ing
in
crea
ses
Ato
mic
rad
ius
incr
ease
s
Ion
ic s
ize
incr
eas
es
Ion
izat
ion
en
erg
y d
ecre
ases
Ele
ctro
neg
ativ
ity
dec
reas
es
1A
2A 3A 4A 5A 6A 7A
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