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Dr. S. M. Condren
Chapter 8
Electron Configuration and Periodicity
Dr. S. M. Condren
Orbitals
• region of probability of finding an electron around the nucleus
• 5 types => s p d f g
• maximum of 2 electrons per orbital
Dr. S. M. Condren
Pure Atomic Orbitals
shape # of orbitals / energy level
s spherical 1
p dumbbell 3
d complex 5
f very complex 7
g extremely complex 9
Dr. S. M. Condren
Pauli Exclusion Principle
Dr. S. M. Condren
Electronic Configurations
• The shorthand representation of the occupancy of the energy levels (shells and subshells) of an atom by electrons.
Dr. S. M. Condren
Electronic Configuration
shells => energy levels
subshells => orbitals
Dr. S. M. Condren
Dr. S. M. Condren
Regions by Electron Type
Dr. S. M. Condren
Electron Filling Order Diagram
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
5s 5p 5d 5f
6s 6p 6d
7s 7p
Start here
Dr. S. M. Condren
Electronic Configuration
H atom
1 electron
1s1
Dr. S. M. Condren
Electronic Configuration
He atom
2 electrons
1s2
Dr. S. M. Condren
Electronic Configuration
Li atom
3 electrons
1s2, 2s1
Dr. S. M. Condren
Electronic Configuration
Cl atom
17 electrons
1s2, 2s2, 2p6, 3s2, 3p5
Dr. S. M. Condren
Electronic Configuration
As atom
33 electons
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p3
or
[Ar] 4s2, 3d10, 4p3
Dr. S. M. Condren
Mn: [Ar]4s2 3d?
How many d electrons does Mn have?
4, 5, 6
Dr. S. M. Condren
Dr. S. M. Condren
Electronic Configuration
negative ions
add electron(s), 1 electron for each negative charge
Dr. S. M. Condren
Electronic Configuration
S-2 ion
(16 + 2)electrons
1s2, 2s2, 2p6, 3s2, 3p6
Dr. S. M. Condren
Electronic Configuration
positive ions
remove electron(s), 1 electron for each positive charge
Dr. S. M. Condren
Electronic Configuration
Mg+2 ion
(12-2)electrons
1s2, 2s2, 2p6
Dr. S. M. Condren
How many valence electrons are in Cl, [Ne]3s2 3p5?
2, 5, 7
Dr. S. M. Condren
For Cl to achieve a noble gas configuration, it is more likely that
electrons would be added
electrons would be removed
Dr. S. M. Condren
Dr. S. M. Condren
Trends in thePeriodic Table
• atomic radius
• ionic radius
• ionization energy
• electron affinity
Dr. S. M. Condren
Atomic Radius
decrease left to right across a period
as nuclear charge increases, number of electrons increase;
however, the nucleus acts as a unit charge while the electrons act independently, pulling electrons towards the nucleus, decreasing size
Dr. S. M. Condren
Atomic Radius
increase top to bottom down a group
each additional electron “shell” shields the outer electrons from the nuclear charge
Zeff = Z – Swhere Zeff => effective nuclear charge
Z => nuclear charge, atomic number
S => shielding constant
Dr. S. M. Condren
Atomic Radius
• increases from upper right corner to the lower left corner
Dr. S. M. Condren
Atomic Radius vs. Atomic Number
Dr. S. M. Condren
Atomic Radius
Dr. S. M. Condren
Ionic Radius
• same trends as for atomic radius
• positive ions smaller than atom
• negative ions larger than atom
Dr. S. M. Condren
Ionic Radius
Isoelectronic Series
• series of negative ions, noble gas atom, and positive ions with the same electronic confiuration
• size decreases as “positive charge” of the nucleus increases
Dr. S. M. Condren
Ge is a semiconductor. If half of the Ge atoms of a sample of Ge are replaced with Ga atoms, with what element should the other half of the Ga atoms be replaced in order for this new compound to be isoelectronic with Ge?
Sn, As, Se
Dr. S. M. Condren
Ionization Energy• energy necessary to remove an electron to
form a positive ion• low value for metals, electrons easily
removed• high value for non-metals, electrons
difficult to remove• increases from lower left corner of periodic
table to the upper right corner
Dr. S. M. Condren
Ionization Energies
first ionization energy
• energy to remove first electron from an atom
second ionization energy
• energy to remove second electron from a +1 ion
etc.
Dr. S. M. Condren
Ionization Energy vs. Atomic Number
Dr. S. M. Condren
Electron Affinity
• energy released when an electron is added to an atom
• same trends as ionization energy, increases from lower left corner to the upper right corner
• metals have low “EA”
• nonmetals have high “EA”
Dr. S. M. Condren
Magnetism
Result of the spin of electrons
diamagnetism - no unpaired electrons
paramagnetism - one or more unpaired electrons
ferromagentism - case of paramagnetism where the substance retains its magnetism
Dr. S. M. Condren
Magnetism
Paramagnetism
Ferromagnetism
Without applied field Without applied field
With applied fieldWith applied field