Week 13 Flashcards
Core electrons
Inner electrons
Held tightly to the nucleus
Do not take part in bonding
Valence electrons
Electrons in outer shell
Held less tightly due to shielding from core electrons
Participate in bonding and responsible for a lot of chemistry
Shielding
Core electrons repel valence electrons
They act like a shield to prevent the outer electrons feeling the full charge of the nucleus
Z eff number
Z is nuclear charge also know as atomic number or the number of protons
Effective nuclear charge = Z eff
- attraction felt by the valence electrons
Z eff = Z - S
S = number of core electrons
Z eff and atomic radius
As Z eff increases electrons are held more tightly into the nucleus
Smaller atomic radii
Z eff decreases to bottom left
Atoms get smaller across a period
Atoms get larger down a group
Ionisation energy
Ion - atom or compound with an overall charge
Ionisation energy - kJ/mol
When Z eff increases attraction is stronger - ionisation energy increases across a period
When electrons are close to the nucleus attraction is stronger - ionisation energy decreases down a group
Electron affinity
amount of energy released when an electron attaches to a neutral atom or molecule in its gaseous state to form an anion
Photoemission spectroscopy
Measures energy of ejected electrons
Light only penetrates into the material a few nm so surface analysis technique
Non destructive
Very sensitive
Trace analysis
High resolution
XPS vs UPS
X ray photoelectric spectroscopy probes core electrons
Ultraviolet photo electron spectroscopy probes valence electrons and chemical bonding