Week 3 Flashcards
The fundamental of an electron is…
determined Electrostatic attraction to nucleus, because it confines the wave to the nucleus
Fundamental energy
The lowest energy level for any standing wave
electron density is given by…
the square of a wavefunction
1s orbital has
no node, lowest energy
2s orbital has
1 spherical node,
3s orbital has
2 spherical nodes
Principle quantum number, n
determines the energy (size or shell) of the electron wavefunction.
nodes = n-1
2p orbital has
1 planar node
3p orbital has
2 nodes: 1 planar and 1 spherical
3d orbital has
2 planar nodes
magnetic quantum numbers for 2p and 3p
-1, 0, 1
magnetic quantum numbers for 3d
-2, -1, 0, 1, 2
More linear nodes leads to
shorter wavelength, and thus higher angular momentum
Angular momentum quantum number, l
may take on any value between 0 and n-1
determines the shape (or subshell) and the # of planar nodes
ml
determines orientation,
There is one s orbital, three p orbitals, five d orbitals in any one set.
spin quantum number ms
Describes the “spin” of the electron
The Pauli Exclusion Principle
no two electrons in an atom may be in the same quantum state
so,
no two electrons can have the same four quantum numbers, n, l,ml, and ms
The Aufbau Principle
electrons in atoms (and molecules) generally exist in their lowest possible energy state - ground state
Electrons generally adopt the lowest possible energy configuration
For multi-electron systems, n is no longer sufficient to predict energy levels. We now need to consider:
Electron-electron repulsion
Orbital Shielding
Electron-electron repulsion
When we have more than one electron, the electrons within an orbital repel each other.
Orbital Shielding
When an orbital is occupied, it shields the interaction of the outer orbital with the nucleus. This alters the energy levels of the orbitals
For orbitals of equal n, those nearest the nucleus have…
the lowest energy
Hund’s rule
The lowest energy electron configuration in orbitals of equal energy is the one with the maximum number of unpaired electrons with parallel spins
Valence electrons
important in the formation of chemical bonds. They will lie in the same group in the periodic table, and form compounds with the same stoichiometry.
Noble gases are unreactive because they contain filled electron shells.
Effective nuclear charge (Zeff)
positive charge felt by an electron in a multi-electron atom
Electrons in the outer orbitals are partially shielded from the nuclear charge resulting in a weaker attraction and a lower Zeff
Atomic radii
Across a period, Zeff increases
* smaller radius
* high ionisation energy
Down a group, electrons are added to orbitals that are further from the nucleus
* larger radius
* low ionisation energy
Anionic radii
When forming an anion, electrons are usually added to the same orbital:
Z is unchanged
Zeff is unchanged
More electrons > more electron repulsion
Cationic Radii
When forming a cation, electrons are removed from the outer orbital
Now the valence orbital is closer to the nucleus > cation is smaller than atom
Ionisation energy (Ei)
the amount of energy required to remove an electron completely from an atom.
Ionisation requires input of energy, so ionisation energy will always be positive.
Larger Zeff means electrons…
are held more tightly to nucleus thus are harder to remove
higher ionisation energy
Electron affinity (Eea)
The energy change when an electron is added to an atom in the gas phase.
If energy is released ➟ atom has an affinity for electrons, and it has a negative electron affinity
Metals Vs. Non-metals (electrons)
Non metals: Elements have an affinity for electrons (readily gain electrons)
Metals: Elements have a very low ionisation energy (readily lose electrons)
