2.2 Foundations In Chemistry 5.1-6.4 Flashcards
Ionisation
A process in which atoms lose or gain electrons and become ions
First ionization energy definition
The energy required to remove one mole of electrons from one mole of gaseous atoms to produce one mole of gaseous cations
M(g) —> M^+ (g) + e^- (g)
Second ionization energy definition
Involved the removal of a second electron
M^+ (g) —> M^2+ (g) + e^- (g)
Evidence for energy levels
Plotting the successive ionisation energies of an element clearly shows the existence of different energy levels and the number of electron in each
Successive ionisation energies increase as more electrons are removed
Large jumps in the ionisation energy reveal where electrons are being removed from the next principal energy level
What are the 4 sub levels
S p d f
Max number of electrons for each sub level
S- 2
P- 6
D- 10
F- 14
Principal energy levels’ sub levels and max electrons
1- 1s -2
2- 2s 2p -8
3- 3s 3p 3d -18
4- 4s 4p 4d 4f -32
Order of energy sub levels
1s 2s 2p 3s 3p 4s 3d 4p 4d 4f
The Aufbau principle
the lowest energy sub levels are occupied first
Who developed the Aufbau principle
Niels Bohr
Why does the 4s sub level fill up before the 3d
It’s lower in energy
Hydroxide
OH-
Sulphate
SO4^2-
Carbonate
CO3^2-
Nitrate
NO3^-
Ammonium
NH4^+
Silver
Ag+
Electron orbitals
It is impossible to exactly locate the position of an electron within an energy sub level. By measuring the electron density around the nucleus, is possible to define regions where electrons are most likely to be found at any one time.
Each energy sublevel has one or more orbitals, each one can contain a maximum of two electrons
Name the sublevels, the number of orbitals and the maximum number of electrons within them
S – 1– 2
P – 3–6
D – 5–10
F – 7–14
The Pauli exclusion principle
States that each orbital may contain no more than two electrons
Spin
The Pauli exclusion principle introduces a property of electrons called spin, which has two states: up and down. The spins of electrons in the same orbital must be opposite
Spin diagram
Shows how the orbitals are filled. Orbitals are represented by squares, and electrons by arrows pointing up or down
Rules for filling electrons in spin diagrams
When two electrons occupy a p-sub level, they could either completely fill the same p orbital or half fill two different P orbitals
Hund’s rule states that the single electrons occupy all empty orbitals within a sub level before they start to form pairs in orbitals
What happens when two electrons are in the same orbital
There is repulsion between them due to their negative charges
The most stable configuration is with single electrons in different orbitals