L5 - Electronic Configuration of the Atom (1) Flashcards
What observations does the quantum theory explain that classic mechanics cannot?
- Spectra of light emitted by atoms; quantisation of energy and energy levels
- Electrons in an atom are stable and stay in their orbitals
- Wave-particle duality: light can behave as if made up of photons with energy depending on frequency
State the Uncertainty Principle.
“Can never know both the exact location and velocity of a subatomic particle at the same time.”
Electrons can be described as _____ by the ___________ ________.
Electrons can be described as waves by the Schrodinger equation.
(A mathematical function that describes an electron’s properties in terms of quantum numbers).
Describe a Hydrogen Spectrum.
- Electrons in an atom are in stable energy levels
- Absorption of a photon of light allows an electron to jump up to a higher level
- Moving down to a lower energy level emits a photon of light
- Measuring the energy of a photon allows the energy difference between levels to be determined; shows that energy levels are not equally spaced
Define Ionisation Energy.
A measure of the amount of energy needed to remove electrons from atoms (or ions).
Define First Ionisation Energy.
The energy required to remove one mole of electrons (to infinity) from one mole of gaseous atoms to form one mole of gaseous positive ions.
Explain why ionisation energies are positive.
- As electrons are negatively charged and protons in the nucleus are positively charged, there will be an attraction between them
- Energy must be added to the system to pull the electron away
Explain the relationship between nuclear charge and ionisation energy.
- The greater the pull of the nucleus, the harder it will be to pull an electron away from the atom
- Hence, the higher the nuclear charge, the higher the ionisation energy
Define Electron Affinity.
The amount of energy needed to add electrons to atoms / ions.
Define First Electron Affinity.
The energy required to add one mole of electrons to one mole of gaseous atoms to form one mole of gaseous negative ions.
Why are First Electron Affinities negative?
First Electron Affinities are negative, indicating energy is released on addition of the electron.
Describe the relationship between Electron Affinity and the ions formed.
The more negative the electron affinity, the more stable the negative ion that is formed.
Explain trends (Atomic Size, First Ionisation Energy, First Electron Affinity) in the periodic table.
- Atomic Size: Increases down, and towards the left
- First Ionisation Energy: Increases up, and towards the right
- First Electron Affinity: Becomes more negative up, and towards the right
Describe Quantum Numbers and explain what information they provide.
- Identify the various energy levels available within the atom in which the electron can reside
Identification numbers: ‘address’ for each electron in an atom:
1) Specify the position (or location) of an electron in an atom
2) Predict the direction of spin / rotation of the electron
3) Determine the energy and angular momentum of the electron
4 Quantum Numbers are required to specify the character of an electron. State these.
- Principal Quantum Numbers (n)
- Azimuthal or Subsidiary Quantum Numbers (l)
- Magnetic Quantum Numbers (m)
- Spin Quantum Numbers (s)
What is an orbital?
A region in space where there is a given (usually 95%) probability of finding a particular electron.
(Cannot specify the definite / exact position of an electron in an atom).
In poly-electron atoms, principal energy levels are called ______.
Shells
What letters are principal energy levels referred to by?
K, L, M, N
n = ?
A number greater than 0.
A group of orbitals with the same energy (equivalent) is called a ________.
Subshell
l = ?
A value from 0 to (n-1).
What letters are designated to the different sub-shells?
s, p, d, f
What do the Principal Quantum Numbers (n) indicate?
- Distance of electron from the nucleus: The higher n, the further away the electron is from the nucleus
- Energy of electron: The higher n, the higher energy the electrons = less tightly held so they are easier to remove
- Number of electrons a shell can hold: n can have 2n^2 electrons
What do the Azimuthal Quantum Numbers (l) indicate?
The sub-shell an electronic in:
- s: sharp
- p: principal
- d: diffuse
- f: fundamental
Higher l, results in ______ ______.
Higher energy
What is the maximum number of electrons a sub-shell can hold?
Max Electrons = 2(2l+1)
What do the Magnetic Quantum Numbers (m/ml) represent?
- Represents the orbitals in a given sub-shell
- Indicates the direction of a particular orbital relative to the magnetic field / axes
Magnetic Quantum Numbers do not indicate ______.
Energy
‘m’ can have an integral value ranging from __________________.
‘m’ can have an integral value ranging from -l through 0 to +l
For a given value of l, total number of m value is?
total number of m = (2l + 1)
What different orbitals exist?
- 1 s orbital
- 3 p orbitals (px, py, pz)
- 5 d orbitals
- 7 f orbitals
What do the Spin Quantum Numbers (s/ms) show?
An electron moving around the nucleus rotates or spins about its own axis (self-rotation) either in a clockwise or anti-clockwise direction.
These directions are described by the spin quantum number.
What values can the Spin Quantum Numbers take?
- Clockwise spinning of electron = + 1/2
- Anticlockwise spinning of electron = - 1/2
Two electrons in the same orbital must have ________ _____.
Opposite spins (Also known as anti-parallel spins)
What does clockwise and anti-clockwise spinning of electrons produce?
Opposite magnetic fields
State the restrictions of Principal, Azimuthal, Magnetic and Spin Quantum Numbers.
- Principal: Positive integer
- Azimuthal: Zero and positive integers less than n
- Magnetic: Integers between -l and +l
- Spin: + 1/2 or - 1/2
