A Level Chemistry Chapter 19 Lattice Energy Detailed Summary Note including the topics - factors affecting lattice energy, enthalpy change, electron affinity, born-haber cycle, ion polarisation, and solubility
-gaseous ions to -lattice energy
ionic solid enthalpy change when 1 mole of an ionic compound is formed from its
-always exothermic gaseousex)ions under standard conditions
Na (g) Cl (g) NaCl (s)
+
- -
I
+
HTatt- -787 kJmol
A
more exothermic lattice energy - stronger ionic bond in the lattice
factors affecting lattice energy
smaller radius - more 1) ionic radius -less exothermic as the ionic radius
exothermic increases
-charge on the ions is more spread out
greater ionic charge - as the ionic radius increases
more exothermic -ions are also further apart from each
other in the lattice
(greater charge -weaker electronstatic forces of
density - stronger attraction b/w oppositely charged ions
forces of attraction -
more exothermic) 2) ionic charge
-more exothermic as ionic charge of the ion increases
-greater ionic charge higher charge density
-
-
-results in stronger electrostatic attraction b/w oppositely
charged ions in the lattice
-always endothermic -enthalpy change of atomisation
(bond breaking- endo enthalpy change when 1 mole of gaseous atom is formed from its
bond forming- exo) elements
ex) Li(s) Li(g) >
H
yat 161kJmol = +
-
I
-electron affinity (EA)
the energy change occurring when a gaseous non-metal atom accepts
one electron
-gaseous atom to first electron affinity (EA1) - when 1 mole of electrons is added
gaseous 1- ions to 1 mole of gaseous atoms to form 1 mole of gaseous 1- ions under
-EA1 is exothermic standard conditions
ex) Cl(g) e Cl (g) EA -348 kJmol
-
-
1
+ 1
1
·
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, subject title check
date
-EA2 and EA3 are second electron affinity (EA2) I
ex) O(g) e O (g) EA -141 kJmol
- - -
t 7
=
always endothermic
O (g) e O (g) EA 798 kJmol
-
- 2 - -
I
+ Y =
+
(bcs energy is 2
required to overcome hence, O(g) 2e O (g) is EA EA -141 798
2
-
1
112
I & =
1
657 kJmol
-
the repulsive forces
= -
b/w incoming electron trends in electron affinities
and negative ion) value of EA1 depends on the attraction between the added electron
and the positively charged nucleus
factors affecting electron affinity
-nuclear charge
greater nuclear charge means greater attractive force b/w the
nucleus and outer electrons
-distance
n greater distance of the outer shell electrons from the positive
nuclear charge, the less attractive forces b/w them
-shielding
greater number of electron shells, the greater the power of inner
shells to shield the outer shell
trends in EA of Group 16 and 17 elements
going down the groups i
trend -outermost e are held less tightly to the -
-more exothermic nucleus as they are further away
across a period -no. of e shells increases causing shielding
- -
-less exothermic -gets more difficult to add an e
-
down the group -less energy is releases upon adding e
-
-fluorine is an exception bcs it has very small atomic radius
( e density repulsion)
-
1 v
=
-born-haber cycle
-H
ions in ionic compound latt
3
gaseous state
> inte
-
Art elements in their
(multiple steps) standard state
Copyright 2021. 해움. All rights reserved.
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