23. Energetics 2

Question 1

Define enthalpy change of atomisation

Answer 1

The enthalpy change when 1 mol of gaseous atoms is formed from a substance under standard conditions.

Question 2

Define lattice enthalpy

Answer 2

The enthalpy change when 1 mol of an ionic solid is formed from its gaseous ions under standard conditions.

Question 3

Define first electron affinity

Answer 3

The energy change when 1 mol of electrons is added to 1 mol of gaseous atoms to form 1 mol of uninegative ions.

Question 4

What are the factors affecting electron affinity?

Answer 4

Nuclear charge: increased charge density causes greater attraction between nucleus and valence electrons, new electron attracted more easily, MORE exothermic EA

Ionic radius: increased distance decreases attraction, LESS exothermic EA

Shielding: increased number of shells, decreases attraction, LESS exothermic EA

Question 5

What are the trends in electron affinity down the group?