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Atomic Radii
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 Angstrom
Li
Na
K
Rb
Cs
La
XeKr
Zn
Cl
FHe
H
3dtransition
series
4dtransition
series
0.3
0.25
0.2
0.15
0.1
0.05
00 10 20 30 40 50 60
atomic number
atom
ic r
adiu
s
Periodic Trends in Atomic Radii
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 175
Relative Size of Atoms
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 350
Attraction and Repulsion of Electrical Charges
+ +
Particles with opposite charges attract
one another.
Particles with like chargesrepel one another.
- -+ -
Coulombic Attraction
1+ 1-
2+ 2-
4- 3-
2+ 2-
Coulombic Attraction
1) Charge opposites attract like repels 2) Distance
A
B
C
D
Shielding Effect
Kernel electrons block the attractive force of the nucleus from the valence electrons
+nucleus
Valence
Electrons--
--
Electron
Shield
“kernel”
electrons
Shielding Effect and Effective Nuclear Charge
+
__
_
Mg = [Ne]3s2
attractionsrepulsions
Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 336
Mg24.305
12
++++++
++
Decreasing Atomic Size Across a Period
• As the attraction between the (+) nucleus and the (–) valence electrons , the atomic size . Greater coulombic attraction.
• From left to right, size decreases because there is an increase in nuclear charge and Effective Nuclear Charge (# protons – # core electrons).
• Each valence electron is pulled by the full ENC
(ENC = 1)
+++
(ENC = 2)
+
Li Be(ENC = 3)
B1s22s1 1s22s2 1s22s22p1
Li Be B
Sizes of ions: electron repulsion
• Valence electrons repel each other.
9 +
• When an atom becomes a anion (adds an electron to its valence shell) the repulsion between valence electrons increases without changing ENC
• Thus, F– is larger than F
Fluorine atomF
1s22s22p5
9+-
--
-
--
--
-
F1-
1s22s22p6
+1e+1e-- 9+-
--
-
--
--
-
-
Fluorine ionFluoride ion
Atomic Radius of Atoms
Na
K
Rb
Cs
ClSPSiAl
BrSeAsGeGa
ITeSbSnIn
Tl Pb Bi
Mg
Ca
Sr
Ba
Be FONCB
Atomic Radii
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 Angstrom
0.60 0.31
0.95 0.65
1.33 0.99
1.48 1.13
1.69 1.35
1.71 1.40 1.36
0.50 1.84 1.81
0.62 1.98 1.85
0.81 2.21 2.16
0.95
IA IIA IIIA IVA VA VIA VIIA
= 1 Angstrom
Li1+ Be2+
Na1+ Mg2+
Ba2+
Sr2+
Ca2+K1+
Rb1+
Cs1+
Cl1-
N3- O2- F1-
S2-
Se2- Br1-
Te2- I1-
Al3+
Ga3+
In3+
Tl3+
Ionic Radii
Atomic Radii
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 Angstrom
He
Ne
Ar
Kr
Xe
Rn
0.93
1.12
1.54
1.69
1.90
2.20
VIIIA
0.60 0.31
0.95 0.65
1.33 0.99
1.48 1.13
1.69 1.35
1.71 1.40 1.36
0.50 1.84 1.81
0.62 1.98 1.85
0.81 2.21 2.16
0.95
IA IIA IIIA IVA VA VIA VIIA
= 1 Angstrom
Li1+ Be2+
Na1+ Mg2+
Ba2+
Sr2+
Ca2+K1+
Rb1+
Cs1+
Cl1-
N3- O2- F1-
S2-
Se2- Br1-
Te2- I1-
Al3+
Ga3+
In3+
Tl3+
Ionic Radii
Trends in Atomic and Ionic Size
152
186
227
Li
Na
K
60
Li+
95
Na+
133
K+
e
e
e
F-
136
Cl-
181
Br-
195
F
Cl
Br
64
99
114
e
e
e
Metals NonmetalsGroup 1
Al
143
50
ee
e
Group 13 Group 17
Cations are smaller than parent atoms Anions are larger than parent atoms
Al3+
152
Li
60
Li+
e
152
60
Li+
e
e
e
e
Li
Lithium atom
Lithium ion
+
152
Li
Lithium atom
Li
Energy
IA IIA IIIA IVA VA VIA VIIA
0.60 0.31
0.95 0.65
1.33 0.99
1.48 1.13
1.69 1.35
1.71 1.40 1.36
0.50 1.84 1.81
0.62 1.98 1.85
0.81 2.21 2.16
0.95
Li1+ Be2+
Na1+ Mg2+
Cl1-
N3- O2- F1-
S2-
Se2- Br1-
Te2- I1-
Al3+
Ga3+
In3+
Tl3+
Ca2+K1+
Sr2+Rb1+
Cs1+ Ba2+
Li
Na
K
Rb
Cs
ClSPSiAl
BrSeAsGeGa
ITeSbSnIn
Tl Pb Bi
Mg
Ca
Sr
Ba
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
Be B C N O F
= 1 Angstrom
AtomicRadii
IonicRadii
Cations: smaller than parent atoms
Anions: LARGERthan parent atoms
The Octet Rule and Common Ions
Oxygen atomO
1s22s22p4
Fluorine atomF
1s22s22p5
Sodium atomNa
1s22s22p63s1
Magnesium atomMg
1s22s22p63s2
8+-
--
-
- --
-9+-
--
-
--
--
-
11+-
--
-
-
--
--
-
-
12+-
--
-
-
--
--
--
-
11+-
--
-
-
--
--
-
12+-
--
-
-
--
--
-
Oxygen ionO2-
1s22s22p6
Fluorine ionF1-
1s22s22p6
Sodium ionNa1+
1s22s22p6
Magnesium ionMg2+
1s22s22p6
10+-
--
-
-
--
--
-
Neon atomNe
1s22s22p6
+1e+1e-- -1e-1e-- -2e-2e--+2e+2e--
8+-
--
-
- --
-
-
-9+-
--
-
--
--
-
-
Isoelectronic Species
11+-
--
-
-
--
--
-
12+-
--
-
-
--
--
-
Oxygen ionO2-
1s22s22p6
Fluorine ionF1-
1s22s22p6
Sodium ionNa1+
1s22s22p6
Magnesium ionMg2+
1s22s22p6
8+-
--
-
- --
-
-
-9+-
--
-
--
--
-
- 10+-
--
-
-
--
--
-
Neon atomNe
1s22s22p6
IsoelectronicIsoelectronic - all species have the same number of electrons.
Can you come up with another isoelectronic series of five elements?
p = 8n = 8e = 10
p = 9n = 9e = 10
p = 10n = 10e = 10
p = 11n = 11e = 10
p = 12n = 12e = 10
Lewis Structure
Na ClX
o o
o o
ooo H C No
XX
X
X
ClNa H C N
ClNa H C N
Gilbert Lewis
“Lewis Dot Notation”
Atomic Radius vs. Atomic Number
Li
Na
K
Rb
Cs
La
XeKr
Zn
Cl
FHe
H
3dtransition
series
4dtransition
series
0.3
0.25
0.2
0.15
0.1
0.05
00 10 20 30 40 50 60
atomic number
atom
ic r
adiu
s
