Lecture 1: Atomic orbitals and electronic structure of atoms Flashcards
Is an electron a particle or a wave?
Both. Electrons show characteristics of both waves and particles.
What is a wave function?
Psi, Ψ. A wave function contains all the measurable information about the particle, e.g. position, momentum. It is a mathematical entity, so cannot be visualised.
What is Ψ2?
This is the electron density. The probability of finding an electron at a specific distance from the nucleus. The total area under the curve is 1 as the particle must be somewhere in the universe.
What is the radial electron distribution?
4πr2Ψ2. The 4πr2 gives the area. The peak of the radial distribution shows the most likely distance that the electron is from the nucleus. This is the Bohr radius. There is a node on the radial distribution where there is 0 probability that the electron is that distance from the nucleus.
What are the shapes of these atomic orbitals: a) 2s, b) 2p?
a) circular b) two lobes on either side of the nucleus
What is the Aufbau principle?
Electrons placed in orbitals starting with the lowest energy and working up
What is the Pauli exclusion principle?
Two electrons per orbital, spins paired (up and down)
What is Hund’s Rule?
When multiple orbitals of the same energy are available, electrons are distributed among them, spins parallel. This is because electrons repel each other.
What is a covalent bond?
Sharing of electrons between two atoms. It can only form if there are more favourable interactions than unfavourable interactions.
What is electrostatic potential energy?
The attraction between two charges. It is measured in Coulombs. It is E = k x (q1 x q2)/r, where q1 and q2 are the charges and r is the separation distance.
How are atomic orbitals combined to make molecular orbitals?
Their wave functions are added together.
What is the difference between bonding orbitals and anti-bonding orbitals?
Electrons in bonding orbitals are mainly between the two nuclei. The favourable interactions overcome the unfavourable reactions. Electrons in anti-bonding orbitals are not between the two nuclei. They do not help in the formation of a bond and actually hinder it. Anti-bonds are designated with an asterisk, *.
Draw an energy level diagram to show why two hydrogen atoms form a bond to become a hydrogen molecule.
The energy of the H2 molecule is lower than the separate H atoms, so the reaction is favourable.
Draw an energy level diagram to show why two helium atoms do not form a bond to become a helium molecule.
The energy of the helium molecule is not lower than the separate helium atoms, so it is not favourable to form a bond between the atoms.
What is paramagnetism?
When a molecule acts as a magent when in an external magnetic field, but cannot keep the magnetic behaviour when not in an external magnetic field. Paramegnetism results from unpaired electrons.
