1.5 & 1.6: Electronic Configuration Of Atom Flashcards
What are the 2 important concepts of the Quantum Theory?
- Electrons can be described as waves by the Schrondinger equation
- Uncertainty principle
What is the Schrondiger equation?
An equation that describes an electron’s properties in terms of quantum numbers
What is the uncertainty principle?
The idea that both the exact location and velocity of a subatomic particle can never be known at the same time
What are the 3 observations that quantum theory shows and classical mechanisms can’t?
- Spectra of light emitted by atoms
- Stability of atoms
- Wave-particle duality
What does measuring the energy of a photon allow us to determine?
The energy difference between levels - this indicates energy levels are not equally spaced
What is ionisation energy?
The measure of the amount of energy needed to remove electrons from atoms/ions
Define ‘First Ionisation Energy’
The amount of energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous positive ions
What gives us evidence for the arrangement of electrons within an atom?
Patterns in ionisation energies
What is electron affinity?
The amount of energy needed to add electrons to atoms/ions
Define ‘First Electron Affinity’
The amount of energy required to add one mole of electrons to one mole of gaseous atoms to form one mole of gaseous negatively charged ions
Why are first electron affinities always negative?
Energy is released on addition of the electron
What shows the stability of a negative ion?
Electron affinity - the more negative = more stable ion formed
What is the trend in Atomic size:
1. Down a group
2. Across a period
Atomic size increases down a group
Atomic size decreases across a period
What is the trend in first ionisation energy:
1. Down a group
2. Across a period
First ionisation energy decreases down a group
First ionisation energy increases across a period
What is the trend in Atomic size:
1.
What is the trend in Atomic size:
1.
What is the trend in First electron affinity:
1. Down a group
2. Across a period
First electron affinity becomes less negative down a group - less stable ion
First electron affinity becomes more negative across a period - more stable ion
What is an orbital?
A region in space where there is a given (usually 95%) probability of finding a particular electron
Cannot specify the exact position of an electron in an atom
What are quantum numbers?
The various energy levels available within an atom in which electrons can reside
What 3 things do quantum numbers show?
- The position of an electron in an atom
- The direction of spin of the electron
- The energy and angular momentum of an electron
What are the 4 quantum numbers required to specify the character of an atom?
- Principle Quantum Numbers (n)
- Azimuthal or subsidiary Quantum Numbers (l)
- Magnetic Quantum Numbers (m)
- Spin Quantum Numbers (s)
What do principle energy levels/ shells correspond to?
The Principle Quantum Number (n)
What are Principle Quantum Numbers traditionally referred to?
Letters K, L, M …..
Where the K shell n =1
L shell n =2 etc
What happens to energy levels in complex atoms when n increases?
They get closer
What do Principle Quantum Numbers (n) indicate?
- Distance of electrons from nucleus
- Energy of electron
- Number of electrons a shell can hold : 2n²
What is the formula used to determine how many electrons a shell can hold?
2n²
What is a subshell?
A group of orbitals with the same energy
What are subshells described by?
The azimuthal or subsidiary quantum number (l)
What range of values is l always between?
0 to n-1
What letters do the azimuthal or subsidiary quantum numbers correspond to?
Letters s, p ,d, f ……
What 4 things do azimuthal quantum numbers indicate?
- Which subshell an electron is in
- Energy of the subshell
- Shape of the orbitals in the subshell
- Maximum number of electrons a subshell can hold
How can the maximum number of electrons a subshell can hold be worked out?
By equation: 2(2l+1)
Eg. l for d-subshell = 2
Therefore, the number of electrons it can hold = 2(4+1)=10
What shape is an s-orbital (l=0)?
Spherical
What
What shape is a p-orbital (l=1)?
Dumbbell
What shape is a d-orbital (l=2)?
More complex
What shape is a f-orbital (l=3)?
Still more complex
What can the combination of n and l be used for?
To identify a particular subshell and thus describe the location of an electron in the atomic energy level
What do Magnetic Quantum Numbers (m) represent?
The orbitals in a given subshell
What do Magnetic Quantum Numbers (m) indicate and don’t indicate?
Indicate the direction of a particular orbital relative to the magnetic field/axis
Don’t indicate energy
‘m’ can have integral value ranging from –l through 0 to +l. Therefore,
for a given value of l, total number of m value is (2l+1)????????
LEARN THIS
What does the Spin Quantum Number (s) describe?
How an electron, moving around the nucleus, spins about
its own axis (self rotation) either in a clockwise or
anticlockwise direction
(also described as spin up and spin
down)
What are the two possible spin quantum values?
+1/2 (clockwise spinning)
-1/2
(anticlockwise spinning)
What do clockwise and anti-clockwise spinning
electrons produce?
Opposite magnetic fields
What is AUFBAU PRINCIPLE?
Electrons enter the lowest available energy level first
What is MADELUNG’S RULE?
The energy of an atomic orbital increases with increasing n+l. For
identical values of n+l, energy increases with increasing n
What is HUND’S RULE OF MAXIMUM MULTIPLICITY?
When in orbitals of equal energy, electrons will try to remain unpaired.
What is PAULI EXCLUSION PRINCIPLE?
No two electrons can have the same four quantum numbers.
Only two electrons can go in each orbital, providing they are of opposite
spin.
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MEMORISE PAGE 23
What are the electronic configurations of Cr and Cu?
Cr Z = 24 1s2 2s2 2p6 3s2 3p6 4s1 3d5
Cu Z = 29 1s2 2s2 2p6 3s2 3p6 4s1 3d10
How are anions (negative ions) formed?
By adding electrons to atoms
How are cations (positive ions) formed?
By removing electrons from atoms
Where is an electron removed from first and what is an exception to this rule?
The highest occupied orbitals
Transition metals lose s electrons first
What does a large jump between successive ionisation energy indicate
A change in energy level from which the electron has been removed.
What does Diamagntic mean?
There are no unpaired electrons - slightly repelled by magnetic field
What does Paramagnetic mean?
There is at least 1 unpaired electron
Spins align to external magnetic fields
Give an example of a contrast agent used in medical imaging ?
GD3+ (commonly used - 7 unpaired electrons)
Used in MRI scanning image enhancement
