Periodic Properties
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Transcript of Periodic Properties
Periodic Properties
electron configurations propertieshydrogen atom 1 electron
to remove e- nf = ∞
E = x 6.022 x 1023 atomsatom mol
= 1311 kJmol
Z = 1
from ground state ni = 1
2.178 x 10-18 J
E =1nf
2-
1ni
2- RH Z2
nuclear charge1s1
Ionization Energy, I
He+ Z = +2
E =1nf
2-
1ni
2- RH Z2 = 5250 kJ/mol
1s1 E = 5250 kJ/mol
systems with more than 1 electronstudied experimentally ionization reactions
higher nuclear charge lowers orbital energy
-
+
-
2+
stabilizes system
H 1s1 Z = +1 E = 1311 kJ/mol
1. Effect of 2 electrons in same orbital
He 1s2
Z = +2E = 2372 kJ/mol
same nuclear charge-
2+
-
2+ -
orbital energy highere- e- repulsion
less stable
easier to remove e-
He+ 1s1 E = 5250 kJ/mol
2. Effect of electrons in different orbital
LiLi2+
1s2
2s1
Z = +3E = 2954 kJ/molE = 520 kJ/mol
same nuclear charge
3+3+
ground state 2s1
excited state
1s 1s2s 2s
-
-
-
-
inner electrons shielding chargeZeff < Z
3. Effect of orbital shape
LiLi
1s2
1s2
Z = +3E = 341 kJ/molE = 520 kJ/mol
same nuclear charge
ground state 2s1
excited state 2p1
3+
1s
2s
3+
1s2p
-
-
--
-
-
s orbitals penetrating lower energy
determine orbital energiesElectrostatic interactions
1. Greater nuclear charge (Z) lowers energy
2. Electron-electron repulsion raise energy
electrons more difficult to remove
electrons easier to removeelectrons shield Zinner electrons shield better
3. Orbitals with more penetration lower energy
electrons more difficult to removes < p < d < f
Ionization Energy
energy required to remove an e- from gas phase atoms
X+ (g) X2+(g) + e-
first ionization energy I1X (g) X+(g) + e-
second ionization energy I2
lowest I1 Csn = 6highest I1 Hen = 1
I1 decrease Zeff decreases more shielding e-
I1 increase Z increases shielding stays same
core e-
adding valence e-
core e- unchanged
5+
1s2s
2p
10+
-
1s2s
2p
-
-
-
-
-
-
-
-
-
B Ne
-
-
-
-
-
4+
1s2s
Be B
5+
1s2s
2p
-
-
N O
-
-
-
-
-
-
-
e- e- repulsion
Second Ionization Energy I2
Na
I1 I2 I3 I4 I5 I6 I7
MgAlSiPS
Cl
Ar
495
735580780
10601005
1255
1527
4560
14451815157518902260
2295
2665
773011,600
16,10021,200
27,000very difficult to removecore electrons
Atomic Radius
metallic radius Al 143 pm
covalent radiusCl 100 pm
C-Cl 177 pmCl 100 pmC 77 pm
Atomic Radiusincrease in size n dominates
decrease in size
Zeff dominates
Ionic sizes
e-
+ -
isoelectronic series
46 e-
+49 +50 +51 ions get smaller
same # electrons