KA 2: atomic orbitals, electronic configuration and the periodic table Flashcards
what are standing (stationary) waves?
waves that vibrate in time but do not move
what is an orbital?
different sizes and shapes of standing waves possible around the nucleus
What is the max. number of electrons that an orbital can hold
2
Name the four different shapes of orbitals
s,p,d,f
What is “quanta”?
the fixed amount of energy that electrons within an atom have
what can electrons be defined in terms of?
quantum number
For Principal Quantum Number:
-Name the symbol
-Say what values it can have
-What does it do
-What is it related to
-n
-can have values n=1,2,3,4…
-indicates main energy level for an electron
-is related to the size of the orbital
The higher the value of……
n, then the further the electrons are from the nucleus
For Angular Momentum Quantum Number:
-Name the symbol
-What does this determine
-What values can it have
-l
-can have values l=0,1,2,3 (up to n-1)
-it determines the shape of the subshell
For Magnetic Quantum Number:
-Name the symbol
-what values can it take
-what does it determine
-ml
-ml can take values of whole numbers (and zero) between -1 and +1
-determines the orientation of the orbital
How is the second shell organised?
one “s” orbital and three “p” orbitals
Three p orbitals are aligned along perpendicular axes.
For Spin Magnetic Quantum Number:
-what does it determine
-name the symbol
-what values can they take
-the direction of spin
-ms
-takes the values of -1/2 or +1/2
when an orbital contains two electrons they must…
be paired with spins opposed
In s orbitals:
-what is the value of l
-describe the trend
-l=0
-increasing size and energy as n increases
In p orbitals:
-what is the value of l
-what is it’s shape
-how many orbitals
-explain the trend
-l=1
-dumbbell shaped
-3 orbitals corresponding to ml= -1,0,1. These 3 orbitals have the same energy (degenerate)
-Energy and size increases with n(2p<3p<4p)
In d orbitals:
-what is the value of l
-what is it’s shape
-how many orbitals
-explain the trend
-l=2
-more complex dumbbell shapes
-5 orbitals (ml= -2,-1,0,1,2)(degenerate)
-energy and size increases with n (3d<4d)
describe the organisation of the third shell
max. 18 electrons
-2 in the s orbital
-6 in the 3 p orbitals
-10 remaining in the d orbitals (5 d orbitals)
What does degenerate mean?
orbitals that have the same energy
what is the periodic table subdivided into and what does that correspond to?
-s,p,d,f
-corresponds to the outer electronic configurations of these elements
what does each box in box notation represent?
an atomic orbital
what does box notation represent?
The relative energies corresponding to each orbital can be represented diagrammatically using orbital box notation for the first four shells of a multi-electron atom.
What is the order of filling?
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
what does each thing correspond to in spectroscopic notation?
leading numbers=> the n numbers i.e. the shell
letters=> the sub-shell (l numbers)
subscript=> the total number of electrons within that sub-shell
Name the three principles/rules
-The Aufbau Principle
-Hund’s rule
-The Pauli Exclusion Principle
Explain the Aufbau principle
electrons fill orbitals in order of increasing energy
Explain Hund’s rule
when degenerate orbitals are available, electrons fill each singly, keeping their spins parallel before spin pairing starts
Explain the Pauli Exclusion Principle
No two electrons in one atom can have the same set of quantum numbers
as a consequence, no orbital can hold more than two electrons and these electrons have opposite spin
what can the variation in first, second and subsequent ionisation energies with increasing atomic number for the first 36 elements can be explained by?
in terms of the relative stability of different subshell electronic configurations
what does the variation give evidence for?
allows anomalies in the ionisation energies
There is a special stability associated with half-filled and full subshells
Explain the trend
the more stable the electronic configuration, the higher the ionisation
What can be used to predict the shapes of molecules and polyatomic ions?
VSEPR (valent shell electron pair repulsion)
how do you find the total number of electron pairs surrounding a central atom?
-taking the total number of valence (outer) electrons on the central atom and adding one for each atom attached
-adding an electron for every negative charge
-removing an electron for every positive charge
-dividing the total number of electrons by two to give the number of electron pairs
how can the shape of the molecule be determined?
by the atoms present based on the arrangement of electrons
name the 5 different arrangements of electron pairs around a central atom
-linear for two electrons pairs
-trigonal planar for three
-tetrahedral for four
-trigonal bipyramidal for five
-octrahedral for six
electrons pairs are…
negatively charged and repel each other
whats one reason that electron pairs are organised the way they are?
to minimise repulsion/maximise separation
what is the order of electron pair repulsions
non-bonding/non-bonding>non-bonding pair/bonding pair>bonding/bonding pair
what does it mean if a molecule, or ion, has lone pairs on the central atom?
explain why this occurs
the shapes are slightly distorted away from the regular shapes
this is because of the extra repulsion caused by the lone pairs
what is the lone-pair order?
bond pair-bond pair<lone pair-bond pair<lone pair-lone pair
what do the different strengths of electron pair repulsion account for?
slight deviations from expected bond angles in molecules such as NH3 and H2O
