2. TOPICS TO BE COVERED:-
ELECTRON GAIN ENTHALAPY
• FACTORS AFFECTING ELECTRON GAIN ENTHALAPY (EGE)
• SIZE
• SHEILDING EFFECT
• PENETRATION EFFECT
• ELECTRONIC CONFIGURATION
• QUESTION & ANSWERS
3. ELECTRONGAINENTHALPY:-
• EGE means that energy released when isolated gaseous atom gains electron
• More –ve the EGE , more easily atom is gaining electron
• Less –ve the EGE , it is hard for atom to gain electron relatively
• For metals and noble gases EGE is +ve
• Note:- Generally more the electronegativity(EN-) , more the EGE.
4. ELECTRON GAIN ENTHALPY FLOW CHART:-
MORE –VE -> atom will gain electron easily -> non- metals
LESS –VE -> atom will not gain electron easily -> not a good non-metal
If EGE is +ve -> atom will not gain electron -> metals and noble gases
Note:-
5. FACTORS AFFECTING ELECTRON
GAIN ENTHALPY
• The distance between the nucleus and the final shell that accepts incoming electrons grow as the atom’s size
grows.
• This will decrease the force of attraction between the nucleus and incoming electron.
• Thus, the electron gain enthalpy results in less negative.
• with the increase in atomic size, the nucleus’s attraction for the incoming electron decreases. Therefore, the
electron gain enthalpy results in less negative.
• Chlorine holds the most negative electron gain enthalpy.
• more the size of atom, more the number of electron.
• lesser the size of atom, less the number of electron.
1.
Size
6. 2. Shielding
Effects
• As the nuclear charge increases, the force of attraction between the incoming electron and nucleus
increases, which is the highest electron gain enthalpy. Therefore, the enthalpy becomes more
negative.
• As the nuclear charge decreases, the force of attraction between the incoming electron and nucleus
decreases, which is the lowest electron gain enthalpy. Therefore, the enthalpy becomes less negative.
7. 3. Electronic
Configuration
• Elements with exactly either half-filled or completely filled orbitals are very stable.
• You have to supply the energy to add an electron.
• As a result, their electron gain enthalpy is quite positive. The electron gain enthalpy becomes
less negative while going from top to bottom in a group.
• At the same time, it becomes more negative in going from left to right in a period.
8. 4. Penetration
effect
• The nucleus is made up of positively charged particles and electrons are negatively charged
particles which is pretty close to each other by the attraction of the nucleus.
• The electrons repel each other but at the same time, they are attracted by the nucleus.
• This balance between attractive forces and repulsive forces is known as shielding.
• Whereas the ability which allows an electron to get close to the nucleus is known as
penetration.
9. Trends Of Electron Gain
Enthalpy
• In a period EGE increases from left to right as size of atom decreases.
• In a group EGE decreases from top to bottom as size of atom increases.
11. Q1. When the atomic radius increases, electron gain enthalpy
__.
(a)Increase
(b)Decrease
(c)No change
(d)None of the above
Answer: (b) When the atomic radius increases, electron gain
enthalpy decreases.
12. Q2. Which group of compounds have the largest electron
gain enthalpy?
(a)Alkali metals
(b)Alkaline earth metals
(c)Halogen family
(d)None of the above
Answer: (c ) Halogen family compounds have the largest
electron gain enthalpy.
13. Q3. Which of the following factors affect the electron gain
enthalpy of an element?
(a)Nuclear charge
(b) Atomic size
(c) Both (a) and (b)
(d) None of the above
Answer: (c ) Nuclear charge and atomic size affect the
electron gain enthalpy of an element.
14. Q4. Fluorine has a lower electron affinity than chlorine
because of
(a)Small size and high density of fluorine
(b)Small size and high density of chlorine
(c) Large size and low density of fluorine
(d)Large size and low density of chlorine
Answer: (a) Fluorine has a lower electron affinity than
chlorine because of small size and high density of fluorine.
15. Q5. What is electron gain enthalpy?
Answer: Electron gain enthalpy refers to
the amount of energy released or
absorbed when an electron is added to an
isolated gaseous atom. Its unit is kJ/
16. Q6. Why is the electron gain enthalpy of chlorine more
negative than fluorine?
Answer: The electron gain enthalpy of chlorine is more
negative than fluorine because fluorine is much smaller than
chlorine. There is strong interelectronic repulsion in the
relatively small 2p orbitals of fluorine. Thus, the incoming
electron will not experience much attraction. Hence, the
electron gain enthalpy of chlorine is more negative than
fluorine.
17. Q7. Why is electron gain enthalpy of noble gases positive?
Answer: The electron gain enthalpy of noble gases is positive
because noble gases have completely filled valence orbitals,
and there is no vacant space for additional electrons.
Additional electron is placed in the subsequent higher orbital
as energy is supplied for the addition of additional electrons.
Thus, it is positive.
18. Q8. Why does electron gain enthalpy decrease down
the group?
Answer: Electron gain enthalpy decreases down the
group because as we move down the group, the size of
an element increases, and the effective nuclear charge
decreases. Due to this, the incoming electron will
experience less attraction. Thus, electron gain enthalpy
decreases as we move down the group.
