Periodicity

Question 1

Ionisation Energy

Answer 1

Ionisation Energy or Ionisation Potential of a species A can be defined as the molar internal energy change, ΔU, for the reaction: A(g) → A+(g) + e-(g) at 0 K, reactants and products being in their standard states. We often assume that ΔH(298 K)  ΔU(0 K).

Question 2

Bond dissociation energy

Answer 2

Bond dissociation energy is defined as the enthalpy change associated with the reaction in which one mole of the bond is homolytically broken, reactants and products being in the ideal gas state at 1 bar and 298.15 K. e.g. for methane, the C-H dissociation energyy refers to: CH4(g) → CH3.(g) + H.(g)

Question 3

Boiling point

Answer 3

Boiling point of a substance is the temperature at which the vapour pressure of the liquid is equal to the pressure exerted on it by the surroundings.

Question 4

Melting point

Answer 4

Melting point is the temperature at which the solid and liquid forms of a pure substance can exist in equilibrium.

Question 5

missing

fill

Answer 5

intro lec until long form

Question 6

Zeff value across a row

Answer 6

1. more protons in nucleus Zeff increases across a row
2. more electrons in valence shell Zeff will decrease due to e- repulsion

1 beats 2 so Zeff will increase

Question 7

Zeff value down a group

Answer 7

Zeff initially increases then remain constant

Question 8

Slaters rule apply only for

Answer 8

s and p block

Question 9

Slater’s rules

Answer 9

s is screencing constant = # of e- + shielding contribution depending on the rule

Z atomic number

Question 10

Ionization energy graph

Answer 10

Question 11

Ionization energy discontinuation

1) Be and B
2) N and O

Answer 11

1. s to p ( p has a node) shielded Zeff lower so IE lower
2. Energy K known as exhange energy per pair

Question 12

Ionization energy down a group

Answer 12

Question 13

ionization energy down a group exceptions

Answer 13