Periodic Properties electron configurations properties hydrogen atom1 electron to remove e - n f =...
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Transcript of Periodic Properties electron configurations properties hydrogen atom1 electron to remove e - n f =...
Periodic Properties
electron configurations properties
hydrogen 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 =1
nf2
-1
ni2
- RH Z2
nuclear charge
1s1
Ionization Energy, I
He+ Z = +2
E =1
nf2
-1
ni2
- RH Z2 = 5250 kJ/mol
1s1 E = 5250 kJ/mol
systems with more than 1 electron
studied 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 = +2
E = 2372 kJ/mol
same nuclear charge
-
2+
-
2+ -
orbital energy higher
e- e- repulsion
less stable
easier to remove e-
He+ 1s1 E = 5250 kJ/mol
2. Effect of electrons in different orbital
Li
Li2+
1s2
2s1
Z = +3
E = 2954 kJ/mol
E = 520 kJ/mol
same nuclear charge
3+3+
ground state 2s1
excited state
1s 1s
2s 2s
-
-
-
-
inner electrons shielding chargeZeff < Z
3. Effect of orbital shape
Li
Li
1s2
1s2
Z = +3
E = 341 kJ/mol
E = 520 kJ/mol
same nuclear charge
ground state 2s1
excited state 2p1
3+
1s
2s
3+
1s
2p
-
-
--
-
-
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 Z
inner electrons shield better
3. Orbitals with more penetration lower energy
electrons more difficult to remove
s < 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 = 6
highest 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+
1s
2s
2p
10+
-
1s
2s
2p
-
-
-
-
-
-
-
-
-
B Ne
-
-
-
-
-
4+
1s
2s
Be B
5+
1s
2s
2p
-
-
N O
-
-
-
-
-
-
-
e- e- repulsion
Second Ionization Energy I2
Na
I1 I2 I3 I4 I5 I6 I7
Mg
AlSi
P
S
Cl
Ar
495
735
580
780
1060
1005
1255
1527
4560
1445
1815
1575
1890
2260
2295
2665
7730
11,600
16,100
21,200
27,000very difficult to removecore electrons
Atomic Radius
metallic radius Al 143 pm
covalent radiusCl 100 pm
C-Cl 177 pm
Cl 100 pm
C 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