Chemical
Energetics
, Chemical
AHat)
Enthalpy change of Atomisation : The amount of
energy
absorbed
when I mole of
Energetic
gaseous
atoms is from its element under standard conditions
e .
g
1 ac Nacgi YC >
Clig) 02(g) <Og1 Standard conditions
= 298K P - 1 atm
concentration = moldm
Lattice (DHP lat) The amount of energy released when 1 mol
: of
energy an
ionic compound is formed from its gaseous ions under standard conditions
NatcicNaChagy Mg
+
e .
g (g) (g) Mg2 ci <
MgCl2 + O <
MgO
factors
affecting lattice
Energy
·
DHlat &
Charge
radius
Electron affinities EA : -
1st electron
affinity :
Amount of
energy
released or absorbed when 1 mol of
of electron to of
gaseous atom
gain I mol make I mol -I
charged gaseous anions
e
g O(g) e-
0ig) Chigi +
Clig)
-
+ e
> >
.
O .
Why are all electron affinities after 1st electron
affinity positive (i .
e absorb
energy
endo
.
Ans .
Energy is needed to overcome repulsion between electron specie
rends in electron affinities Grou 16 and 1 Less exothermic than expected because radii are
M
to small , which leads to electron repulsion
greater
Across period 1st affinity gets
·
,
electron more exothermic
nuclear increases
charge
-
effect remains
Shielding constant
-
Atomic radius
-
decreases
Y
Across period Therefore released
gets Down the
group gets
addition of
-
,
more
energy on
more exothermic Less exothermic electron
Energetics
, Chemical
AHat)
Enthalpy change of Atomisation : The amount of
energy
absorbed
when I mole of
Energetic
gaseous
atoms is from its element under standard conditions
e .
g
1 ac Nacgi YC >
Clig) 02(g) <Og1 Standard conditions
= 298K P - 1 atm
concentration = moldm
Lattice (DHP lat) The amount of energy released when 1 mol
: of
energy an
ionic compound is formed from its gaseous ions under standard conditions
NatcicNaChagy Mg
+
e .
g (g) (g) Mg2 ci <
MgCl2 + O <
MgO
factors
affecting lattice
Energy
·
DHlat &
Charge
radius
Electron affinities EA : -
1st electron
affinity :
Amount of
energy
released or absorbed when 1 mol of
of electron to of
gaseous atom
gain I mol make I mol -I
charged gaseous anions
e
g O(g) e-
0ig) Chigi +
Clig)
-
+ e
> >
.
O .
Why are all electron affinities after 1st electron
affinity positive (i .
e absorb
energy
endo
.
Ans .
Energy is needed to overcome repulsion between electron specie
rends in electron affinities Grou 16 and 1 Less exothermic than expected because radii are
M
to small , which leads to electron repulsion
greater
Across period 1st affinity gets
·
,
electron more exothermic
nuclear increases
charge
-
effect remains
Shielding constant
-
Atomic radius
-
decreases
Y
Across period Therefore released
gets Down the
group gets
addition of
-
,
more
energy on
more exothermic Less exothermic electron
