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CHM1011
Exam and Study Notes
Table of Contents
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Structure of the Atom
Understanding the Periodic Table
Valency, Lewis Structures & VSEPR
Valance Bond Theory
Molecular Orbital Theory
Gasses & Intermolecular Bonding
Chemical Thermodynamics
Chemical Equilibria
Chemical Kinetics
Extra
Structure of the Atom
 V = c/ λ where c is 3x108 m/s and λ is wavelength (m)
 E = hv where h is 6.63x10-34 J/s and v is frequency (Hz or S-1)
 An orbital is “a region in space occupied by at most, two electrons of opposite spin”
 The 1s atomic orbital is lower in energy than the 2s atomic orbital due to shielding
 Quantum Numbers
o
Name
Symbol
Allowed Values
Property
Principal
n
Positive Integers
Orbital Size
Angular
l
Integers from 0 to
Orbital shape (l
Momentum
n-1
values of 0, 1, 2
and 3 corresponds
to s, p, d and f
orbitals)
Magnetic
ml
-l to l
Orbital orientation
 Nodal planes have 0 amplitude
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o
o
Electrons in 3s has better penetration than 3d or 3p, therefore it is closer to the
nucleus
Electrons in the 3s orbital is said to shield an electron occupying the 3p orbital
 Shielding accounts for the nuclear charge actually experienced by an
electron
Understanding the Periodic Table
 Ground State is the lowest possible energy state for a set of electrons
 Degenerate is a set of orbitals which have the same energy
 Electronic Configurations
o Increasing energy we have (shells):
o 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 4d10, 4f14
o Remember if it’s like 1s22s22p53s2 means the electron in 2p got excited and jumped
into 3s
o Remember [Ar] 4s2 3d10 4p5 still means 7 electrons in outer shell (4 th shell)
 Three principles to follow
o The Aufbau Principle (electrons start from the lowest energy)
 “The building up principle”
 The Aufbau Principle states that the to fill the 3d subshell, the 4s subshell
must have 2 electrons in the subshell first
o Pauli Exclusion Principle(Opposite spins)
 No two electron can have the same spin quantum number if they occupy the
same atomic orbital (so ½ or -½ )
o Hund’s Rule
 When electrons are put into orbitals having the same energy, degenerate
orbitals, one electron is put into each orbital before putting a second
electron into the half full orbitals
 We can answer this question by observing some distinct trends in the periodic table. As a
general rule:
 Atomic radius (bottom left strongest)
o Atomic radius increases right to left across a Period.
o Atomic radius increases down a Group.
o This is related to the increasing Zeff, the effective nuclear charge, which is
related to the number of protons and the number of core electrons, which
are responsible for shielding (aka 'screening') the valence electrons from the
nucleus.
 Ionisation Energy (top right strongest)
o Increases as we move from left to right
o Increases as we move up the groups
o This is related to atomic radii, as atomic size decreases, ionisation increases
as it needs more energy to remove an electron
 To explain polarity, we need to consider the difference in electronegativity between two
bonded atoms. The greater the difference in electronegativity, the more polar the bond.