MgO Electron Affinity: Why is O +737 kJ?

In summary, the conversation discusses the properties and behavior of MgO(s). It is mentioned that the heat of sublimation for Mg is +148 kj, the bond dissociation for O is +249 kj, and the ionization energy for Mg is +2201 kj. There is also a discussion about the electron affinity for O, which is +737 kj. The conversation also touches on the fact that the first electron affinity is exothermic, while subsequent ones are endothermic. There is a question about the logic behind this trend and an explanation is given about the stability of multiply charged ions in solids.
  • #1
osaka
8
0
I have a problem with MgO(s).

Mg(s) → Mg(g) Heat of sublimation = +148 kj

½O2(g) → O(g) Bond dissociation = +249 kj

Mg(g) → Mg2+(g)+ 2e- IE1+IE2= +2201 kj

O(g)+2e- → O2- EA= +737 kj

look at the EA in peiodic table O(EA= -141 kj).
When O charged 2e- it seems to be like F(EA=-328 kj) charged 1e-.
it should be - not +.
but Why EA of O=+737kj ?
 
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  • #2
the first electron affinity is exothermic and after always endothermic
 
  • #3
thank you.
 
  • #4
garytse86 said:
the first electron affinity is exothermic and after always endothermic

But, I would like to know why it is always exothermic and then always endothermic, I am trying to find the logic behind, but I cannot!
 
  • #5
How do you bond an electron to a species that is already negatively charged?
Formally multiply charged ons like O^{2-} exist only in solids (or liquids) where they are surrounded by positive charged ions which provide a potential well to stabilize bonding of the seconde electron.
 
  • #6
Oh Ok, Thank you very much!
 

1. What is electron affinity?

Electron affinity is the amount of energy released when an electron is added to an atom or molecule in its gaseous state.

2. What is the electron affinity of MgO?

The electron affinity of MgO is +737 kJ/mol.

3. Why is the electron affinity of O +737 kJ?

The electron affinity of O is +141 kJ/mol, which means that it takes 141 kJ of energy to add an electron to an O atom. However, when an O atom combines with an Mg atom to form MgO, the resulting molecule is more stable, and thus the addition of an electron releases energy. This results in the higher electron affinity of +737 kJ/mol for MgO.

4. How is the electron affinity of MgO measured?

The electron affinity of MgO is measured experimentally by using a mass spectrometer to determine the energy released when an electron is added to MgO gas, and then comparing it to the energy released when adding an electron to Mg gas. The difference between these two values gives the electron affinity of MgO.

5. What are the practical implications of the high electron affinity of MgO?

The high electron affinity of MgO makes it a stable compound, which is used in various industries such as steel production, agriculture, and medicine. It also has applications in electronic devices, as it is a good insulator and has a high melting point. Additionally, MgO is used in the production of ceramics and as a component in building materials due to its strength and resistance to high temperatures.

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