1. electron configurations nuclear charge
Periodic Properties
properties
electron configurations
nuclear charge
hydrogen atom
1 electron
1s1
Z = 1 1 1
to remove e-
nf = ∞
E =
- RH Z2 -
nf2
ni2
from ground state
ni = 1
E =
2.178 x J
x x 1023 atoms
= 1311 kJ
atom
mol
mol
Ionization Energy, I

2. systems with more than 1 electron
Z = +1
E =
1311 kJ/mol
He+
1s1
Z = +2
E =
5250 kJ/mol - - + 2+ 1 1
= 5250 kJ/mol
E =
- RH Z2 -
nf2
ni2
higher nuclear charge
lowers orbital energy
stabilizes system
systems with more than 1 electron
studied experimentally
ionization reactions

3. Effect of 2 electrons in same orbital1.
Effect of 2 electrons in same orbital
He+
1s1
E =
5250 kJ/mol He
1s2
E =
2372 kJ/mol
Z = +2
same nuclear charge
orbital energy higher - 2+ -
e- e- repulsion 2+ -
less stable
easier to remove e-

4. Effect of electrons in different orbital2.
Effect of electrons in different orbital Li
ground state
1s2
2s1
E =
520 kJ/mol
Li2+
excited state
2s1
E =
2954 kJ/mol
Z = +3
same nuclear charge 2s 2s 1s 1s - - - 3+ 3+ -
Zeff
< Z
inner electrons shielding charge

5. Effect of orbital shape3.
Effect of orbital shape Li
ground state
1s2
2s1
E =
520 kJ/mol Li
excited state
1s2
2p1
E =
341 kJ/mol
Z = +3
same nuclear charge 2s 2p 1s 1s - - - - 3+ 3+ - -
s orbitals
penetrating
lower energy

6. Electrostatic interactions
determine orbital energies 1.
Greater nuclear charge (Z) lowers energy
electrons more difficult to remove 2.
Electron-electron repulsion
raise energy
electrons easier to remove
electrons shield Z
inner electrons shield better 3.
Orbitals with more penetration
lower energy
electrons more difficult to remove
s < p < d < f

7. Ionization Energy
energy required to remove an e-
from gas phase atoms
X (g)  X+(g) + e-
first ionization energy I1
X+ (g)  X2+(g) + e-
second ionization energy I2
lowest I1 Cs
n = 6
highest I1 He
n = 1

8. I1 increase
Z increases
shielding stays same
adding valence e-
core e- unchanged
I1 decrease
Zeff decreases
more shielding e-
core e-

9. 2p 2p - - 2s 2s 1s 1s - - - - - - - 5+
10+ - - - - - - B Ne

10. 2p - 2s 2s 1s 1s - - - - - 4+ 5+ - - - B Be N O
e- e- repulsion

11. Second Ionization EnergyNa
495
4560 Mg
735
1445
7730 Al
580
1815
11,600 Si
780
1575
16,100 P
1060
1890
21,200 S
1005
2260
27,000
very difficult to remove Cl
1255
2295
core electrons Ar
1527
2665

12. Atomic Radius
metallic radius Al
143 pm Cl
100 pm
covalent radius
C-Cl
177 pm Cl
100 pm
77 pm C

13. Atomic Radius
increase in size
n dominates
decrease in size
Zeff dominates

14. Ionic sizes isoelectronic series same # electrons 46 e-+
isoelectronic series
same # electrons
46 e-
+49
+50
+51
ions get smaller