chem help for midterm

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Published on 21 Nov 2011
Western University
Chemistry 1027A/B
WESTERN SOS: CHEMISTRY 1100 Review sheet
Bohr Model
-electron considered to be a particle in the hydrogen atom that orbits around the nucleus in a
circular motion -the electron occupies the ground state (n=1), the lowest energy orbit -electron
can absorb energy and be promoted to a excited state, a higher energy level -excited state is
unstable and as the electron returns to a lower energy level, light is emitted
Quantum mechanical model
- electrons behave as standing waves when bound inside a atom -standing waves mathematically
described as wave functions -each harmonic (frequency) corresponds to a discrete energy level
-nodes: areas where the wave function is zero, electrons will never be found -orbital: area where
an electron is most likely to be
: No two electrons can have the same four quantum numbers
Principe Quantum number, n -the energy level -n= nodes + 1 -as n increase, energy of electron
increases and size of the orbital increases Azimuthal Quantum number, l
-shape of the orbital (sublevels) - l = 0 to (n-1) - l can be 0(s), 1(p), 2(d) and 3(f) Magnetic
Quantum number,
- ms= +1/2 and -1/2 -two electrons in the same orbital must have opposite spin
Atomic orbitals
Relative energies : -unoccupied orbitals of the same quantum number (n) have the same energy
-in occupied orbitals, inner electrons shield outer electrons from the positively
charged nucleus therefore electrons further away feel a reduced attractive nuclear force
Pauli Exclusion Principle
-spatial orientation
- ml= -l...0...+l
-each unique combination of n,l and ml represents one orbital
-all electrons of the same n and l are equal in energy (the orbitals are degenerate)
-each orbital can hold a maximum of two electrons
Spin Quantum number, ms
-spin and magnetism
Aufbau principle:
electrons will occupy lower energy orbitals before filling orbitals of higher
Shapes of Atomic orbitals FILL OUT CHART
Electronic configuration
Valence electrons: electrons with the highest principal quantum number ( not always the
electrons last filled) core electrons: electrons in shells already filled that are not valence electrons
Cations: positively charged ions, electrons generally removed from highest principal quantum
anions: negatively charged ions, electrons added and filled as usual isoelectronic species: have
the same electronic configuration
Orbital diagrams
electrons fill orbitals of equal energy singly, with parallel spins, and only start pairing up after all
these orbitals are half filled
Exceptions: Cr and Cu -in chromium, the six electrons after the [Ar] core are arranged as 4s1 3d5
instead of 4s23d4 -in copper, electrons are organized as [Ar] 3d104s1 -electrons are promoted from
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