Lecture 2 Flashcards
(31 cards)
What is a quantum? (plural: quanta)
A very small piece of energy (usually of a particle) that cannot be divided any further
What are quantum numbers? (describe and list them)
Each electron in an atom has 4 ‘quantum numbers’ which are used to describe: the shell the atom belongs to, the number of orbitals, the exact orbital within a subshell and spin magnetic quantum number which identifies the orientation of the spin
What is the Principal quantum number? (add symbol as well)
Symbol: n, describes the shell an atom belongs to (eg: first shell is n=1, second is n=2, etc etc)
What is the Azimuthal quantum number? (add symbol as well)
Symbol: l (lower case L not i), describes the type of orbital an atom is in, l can range from 0 to n-1 and the value of this is often referred to as a ‘subshell’
What is the Magnetic quantum number? (add the symbol as well)
Symbol: ml, describes the exact orbital within a subshell
What is the spin magnetic quantum number?(add symbol as well)
Symbol: ms, identifies the orientation of the spin angular momentum of each electron (NOT ROTATION OF AN ELECTRON). Can be + 1/2 or - 1/2
What is an orbital?
A function that basically describes when an electron could be in space (pretty much an approximation as we assume electrons are independent of each other)
How do we find an electron somewhere in a space?
We calculate the probability density of an electron’s location (the chance of finding an electron in a specific space) from the orbital(s)
How are s orbitals shaped? (s stands for sharp)
Spherical
How are p orbitals shaped? (p stands for principal)
Dumbbell
How are d orbitals shaped? (d stands for diffuse)
Quite funky weird shapes
What are orbital lobes?
Areas where we find a high probability density for locating electrons, the probability depends on the squared value of the wavefunction so positive and negative signs do not matter (wavefunction depends on the position in relation to the plane)
What is the nodal plane?
Planes that separate the two phases of the wavefunction, electrons have a zero probability of being here (nodal planes need to be preserved when attaching atoms together)
What is Aufbau principle?
Electrons fill orbitals starting with the subshell with the lowest energy and then go up
What is Hund’s first rule?
Orbitals that have the same energy (eg: all 3 p orbitals) are partially filled first with one electron per orbital and then when they are all filled with one, they are then filled with the second, this rule results in the first set of partially filled subshells (eg: 3 electrons in the p orbital) in spin parallel as this results in a lower confirmation of energy
What are core electrons?
Electrons found in the inner shell (do not usually change during reactions)
What are valence electrons?
Electrons found in the outermost shell
What is effective charge? Z(eff)
The charge felt by outermost electrons from the positively charged nucleus
What is covalent radius?
The radius of an atom, we can measure this by attaching the same atom to it and cutting the distance between them
What is the concept of electronegativity?
The tendency of an atom to attract electrons to it in a shared bond, this is influenced by the distance between valence electrons and the nucleus and the effective charge
What do electronegative differences in more than 1.7 mean?
The pull of electrons to one atom is so strong that it leads to the formation of ions
What do electronegative differences in less than 0.7 mean?
The pull of electrons between the atoms is more or less the same and these are covalent bonds
What do electronegative differences between 0.7 and 1.7 mean?
There is a slight pull of electrons towards one atom, leading to polarised bonds but electrons are still shared
What is LCAO
Linear combination of atomic orbitals:
we add or subtract atomic orbitals to each other to form molecular orbitals which leads to in-phase of out-of-phase combinations (also called bonding and antibonding molecular orbitals respectively)
