Week 13

Question 1

Core electrons

Answer 1

Inner electrons
Held tightly to the nucleus
Do not take part in bonding

Question 2

Valence electrons

Answer 2

Electrons in outer shell
Held less tightly due to shielding from core electrons
Participate in bonding and responsible for a lot of chemistry

Question 3

Shielding

Answer 3

Core electrons repel valence electrons
They act like a shield to prevent the outer electrons feeling the full charge of the nucleus

Question 4

Z eff number

Answer 4

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

Question 5

Z eff and atomic radius

Answer 5

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

Question 6

Ionisation energy

Answer 6

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

Question 7

Electron affinity

Answer 7

amount of energy released when an electron attaches to a neutral atom or molecule in its gaseous state to form an anion

Question 8

Photoemission spectroscopy

Answer 8

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

Question 9

XPS vs UPS

Answer 9

X ray photoelectric spectroscopy probes core electrons

Ultraviolet photo electron spectroscopy probes valence electrons and chemical bonding