UNIT 1) 3) Atomic Orbitals and Electron Configuration Flashcards
How can the discrete lines in atomic spectra be explained
The discrete lines observed in atomic spectra can be explained if electrons, like photons, also display the properties of both particles and waves.
Within the atom how do electrons behave
Within the atom , electrons behave as standing (stationary )waves. These are waves that vibrate in time but do not move in space
Different shapes and sizes of these “standing” waves are possible around the nucleus
What are these shapes and sizes known as ?
Different shapes and sizes of these standing waves are possible around the nucleus. These are known as orbitals
Explain what an orbital is
- it is not possible to define a space in time where an electron is found - they are constantly moving
- however the probability of finding an electron within a certain volume of space can be calculated
- : the regions where there is a high probability of finding an electron are called atomic orbitals
Therefore an orbital provides a defined volume of space where there is a high probability of finding an electron
Probability of being able to find an electron in an atomic orbital
In atomic orbitals - there is approximately 90% chance of detecting an electron
How many electrons can a single orbital hold (irrespective to size and shape)
2
Electrons within atoms are said to be _________
- what does this mean
Electrons within atoms are said to be quantised
- this means that they can only posses fixed amounts of energy known as quanta
- as a result electrons can be defined in terms of quantum numbers
What does quantum theory state
Quantum theory states that matter can only emit or absorb energy in small fixed amounts
When an electron in an atom _______ a photon of energy it moves from a lower energy level to a higher energy level. When the electron drops back down energy is _______
When an electron in an atom absorbs a photon of energy it moves from a lower energy level to a higher energy level. When the electron drops back down energy is emitted.
Rings are drawn around the nucleus of the atom to represent energy levels.
- The further away the rings are from the nucleus the ________ the energy
- as energy increases the levels become _______ together until they ________
- The further away the rings are from the nucleus the higher the energy
- as energy increases the levels become closer together until they converge
What is the convergence point
An electron that has enough energy to take it beyond the convergence point has left the atom - this means it has been ionised
Electrons are found in orbitals which are found in sub shells of energy level shells.
Each electron has an “address” how is this defined?
It is defined by a set of 4 quantum numbers
- 1st quantum number /principal quantum number
- 2nd quantum number / angular momentum quantum number
- 3rd quantum number / magnetic quantum number
- 4th quantum number / spin quantum number
1st principle quantum number
- what does this refer to
- what is the symbol
- this refers to the energy shell where the electron is located : refers to the size and energy of the shell
- symbol n
N=1 n=2 n=3 etc
What happens to the size of orbital as value n increases
As value of n increases the size of the orbital also increases
2nd quantum number - angular momentum
- what does this refer to
- symbol
- this is the type of sub shell within the energy level given letters s , p, d , f
- symbol = L
Second quantum number relating to type of sub shell
L= 0 - s sub shell 1 - p sub shell 2 - d sub shell 3 - f sub shell
Summary of principal and angular momentum quantum numbers with sub shell name
LOOK IN NOTES AT TABLE
3rd magnetic quantum number
- what does this refer to
- symbol
- relates to the orientation in space of the orbital
- depend on l because ml takes on any whole number value between -L and +L
So of L=2 ml could be +2,+1,0,-1,-2
So this means there are 5 atomic orbitals for L=2
4th spin quantum number
- determines the direction of the spin, it is therefore called the spin quantum number
Has values of -1/2 or +1/2
Summary : relating quantum numbers table
Look In notes !
Orbital shapes : s orbitals
- describe the shape
- what happen to orbital in higher energy levels
- spherical with size and orbital in higher energy levels ar bigger the the orbital in energy level before it
- energy increases as value of n increase
The first shell has only two electrons so has ____ orbital
The first shell has only two electrons so has 1 orbital (1s)
Shape of orbitals ; p orbitals
- how many orientations
- describe shape /placement
- which energy levels have p orbitals
- have value L =1 so therefore three orientations
corresponding to ml = -1, 0, +1 , p sub shells will have 3 p orbitals px,py,pz - all same shape : approximately dumbbell shaped and at right angles to one another (perpendicular)
- as the first shell has two electrons they go into the s orbital so the second shell and subsequent shells have p orbitals in addition to s
The p orbitals are degenerate ,what does this mean ?
Three p orbitals are degenerate meaning they have the same energy as each other
Drawing and example quantum numbers for for 2p and 3p orbitals
- drawings : look in notes
- quantum numbers for 2p : n=2 , l=1 ml=-1,0,+1
- quantum numbers for 3p : n=3 l=1 ml=-1,0,+1
How many electrons does the second energy shell hold - and how is this split into the orbitals
- the second shell can hold a maximum of 8 electrons
- the s orbital holds 2 of these
- the 3 different p orbitals hold 2 each so in total they hold 6
Therefore the second shell has one s orbital and three p orbitals
Shape of orbitals - d orbitals
- how many orientations
- which energy levels are they in
- are they degenerate
- occur in 5 different orientations corresponding to ml= +2,+1,0,-1,-2 and have labels which come from the complex mathematics of quantum mechanics
- are first orient in 3rd energy level so are in 3rd energy levels and the following ones
- they are degenerate
How many electrons can the 3rd shell hold and how
-the 3rd shell can hold a maximum of 18 electrons. Two of these are in an s orbital and three p orbitals hold another 6. The remaining 10 are in d orbitals (so there must be 5 d orbitals as they hold two electrons each)
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What is electron configuration- and how many ways can it be written
- the arrangement of electrons in the energy levels and orbitals of an atom is called the electronic configuration
- three ways - using quantum numbers, orbital box notation , spectroscopic notation
What are the three rules for writing orbital box notation
- AUFBAU : the aufbau principle states that when electrons are placed into orbitals the energy levels are filled up in order of increasing energy eg : 1s is filled before 2s. The orbitals you need to know in order of increasing energy are 1s, 2s, 2p,3s,4s,3d,4p
- PAULI - the Pauli exclusion principle states that no two electrons in the one atom can have the same set of 4 quantum numbers. As a consequence no orbital can hold more than two electrons and the two electrons must have opposite spins (if the two electrons are in one orbital , then both electrons must have the same quantum numbers n, L and ml, but they will have different spin numbers (either +1/2 or -1/2)
HUND- Hunds rules states that when there are degenerate orbitals in such shells (such as in 2p) electrons fill each one singly with spins parallel before pairing occurs
Writing electrons configuration in spectroscopic notation and orbital box notation
Look at notes / textbook (you should already know how to do this )
The structure of the periodic table depends upon the ___________ ____________ of the elements
The structure of the period table depends upon the electronic configuration of the elements
The chemical properties of an element are dictated by the __________ in _________ shells
Therefore the periodic table relates configuration to __________
The chemical properties of an elements are dictated by the electrons in the outer shells
Therefore the periodic table related configuration to properties
What is s , p , d , f block elements of the periodic table
- these are elements located in in certain block of the periodic table
- s block elements, are where the highest energy level electrons are found in the s subshell
What is ionisation energy
The ionisation energy of an element is the energy required to remove one mole of electrons from one mole of gaseous atoms. The second and subsequent ionisation energies refer to removal of further moles of electrons
Ionisation energy graph and explanation
Notes
There a special stability associated with a filled sub shell or a _____ filled sub shell
There is a social stability associated with a filled sub shell or a half filled sub shell
For example the p sub shell when it contains three or six electrons.
Likewise the d sub shell is most stable when it contains five or ten electrons.
How does more stable electron configuration effect ionisation energy
- the more stable the electron configuration , then the more difficult it is to remove an electron and therefore the ionisation energy is higher
