Atomic orbitals - part 1 Flashcards
Atomic orbital
it is a wave-like function that describes the probability on where an electron lies in the atom
orbitals have
different shapes
why do orbitals have different shapes?
each orbital can contain
two electrons
why do hydrogen electrons have a higher energy than helium electrons .
the energy of the orbital will be different from the orbital for hydrogen because it has double the nuclear charge of hydrogen and the electrons are more strongly attracted to the nucleus.
Hund’s rule
. An atom adopts the electronic configuration that has the greatest number of unpaired electrons in degenerate orbitals.
Regions where an electron is most likely to be found are said to have
high electron density
regions where an electron is unlikely to be
found have low electron density.
the square of the orbital wavefunction gives
the electron density at any location
the probability of finding an electron in a small volume V at any location
the square multiplied by the small volume that we are looking for.
Pauli exclusion rule
no two electrons can have the same four quantum numbers
aufbau principle
in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.
constructively overlap
in phase
destructively overlap
out of phase
Principal Q.N. (N)
determines size and energy
orbital angular
momentum l
Orbital type
(s, p, d, f etc.)
Magnetic ml
Orientation of orbital
s
spin quantum number s
spin
The spin can adopt one of two orientations, distinguished by the ms = ½ quantum nu
same energy
degenerate
as n increases
it is further away from the nucleus
for h
For an H atom, different orbitals with the same value of n have the same energy
RDF
show how the electron density varies with distance from the nucleus and are related to the
squares of the orbital wavefunctions #
radial dependence R(r)
Why is H degenerate ?
It’s only the interaction of multiple electrons in an atom like He, Li, Be, etc. that makes the different angular momenta wave functions differ in energy.
Why is H degenerate ?
It’s only the interaction of multiple electrons in an atom like He, Li, Be, etc. that makes the different angular momenta wave functions differ in energy.
Nodes
A wave function node occurs at points where the wave function is zero and changes signs.
iso-surface plots
show the angular shape and the size of the orbital
Instead we draw an iso-surface joining points of equal probability and
enclosing say 90% of the
electron density
filling orbitals
The 2s orbital always fills before the 2p orbital because in atoms with more than one electron, the 2s orbital is lower in energy than 2p
core electrons
we refer to the filled 1s orbital as a core orbital and the
1s electrons as core electrons.
core electrons are not
involved in chemical bonding
overlap
The RDFs show that a 2s electron has a greater
probability of penetrating through the 1s core than does
the 2p electron
2p vs 2s
On average, a 2s electron feels a larger net positive
charge than a 2p electron and hence is lower in energy.
We say that the 2s electron feels a greater effective
nuclear charge (Zeff) than the 2p electro
