# What is the difference between work function and the ionization energy? [duplicate]

So for a hydrogen atom, an electron at n=1 would require 13.6eV of energy to be excited to the infinite energy level, so thats ionization. Is the work function the energy to overcome the attraction between the ionized electron and the nucleus?

• From Review : If you are not satisfied with the current answers or those in the cited question, and wish this question to be reopened, please explain why these answers fail to answer your question. Mar 26 '17 at 0:07

The work function energy is the minimum energy that an electron need to escape from inside the surface of solid to outside the surface of a solid, the solid being made up of many atoms .
The ionisation energy is the energy that an electron (usually the most loosely bound) needs to escape from the (one) atom completely.

• But isnt removing the electron from the surface to outside of the surface kinda completely removing the electron? Mar 25 '17 at 10:01
• But it is not removing it from an individual atom. In a metal there are free (not bound to a particular atom) electrons. Mar 25 '17 at 10:05

When were talking about the work function, we're usually referring to the surface of a metal, say, Sodium! So the work function would be the minimum energy required to remove an electron from the surface of Sodium. This minimum energy is the energy required for just removing an electron. The electron emitted has 0 kinetic energy.

Think of it this way. This is the energy required by an electron to escape the metal lattice. Whenever atoms of an element combine to form a compound (or lattice), the properties of their electrons is different from what it is in the element's individual atom. The electron in a sodium atom is its own, while in a sodium metal lattice, the electron isn't its own anymore. It is attracted by the other atoms and also repelled by the electrons of the other atoms. In other words its energy changes. That's why the ionisation energy is different from the work function of a metal.

The difference between work function and ionisation energy lies in their definition.

Ionisation energy is the energy required to remove an electron (first ionisation energy is the energy required to remove the outermost electron, second ionisation energy is the energy is the energy required to remove the next and so on so forth) from an isolated, gaseous atom of an element.

The difference is one concerns the surface of the substance while the other concerns an atom of the substance in the gaseous phase.

• Ahhh this makes much more sense, so the work function for sodium let say is still taking an electron from a lower energy to that outside of the metal ? Or is it just the surface electrons at the outermost layer? Mar 25 '17 at 10:43
• @Zefty It (work function) is the energy to remove an electron from the lattice. The electrons in the lattice are those from metallic bonding (usually the outer electrons). Does that clear your doubt? Mar 25 '17 at 13:17
• ok and ionization energy is to remove the electron from an isolated atom? while work function is the electrons in metallic bonding Mar 25 '17 at 22:52
• If asked in an exam you should be saying that work function is the energy required to remove (or free) an electron from the surface of a metal. While Ionisation energy is the energy required to remove an electron (which electron we're removing depends actually <see the answer>) from an isolated gaseous atom. Clear now? Mar 26 '17 at 2:56

Generally the work function is defined for a crystalline solid with a band structure, like a metal. The work function is the energy required to extract an electron from the conduction band to the vacuum. The ionization energy is the energy required to extract an electron from a neutral atom in a gas. As you can see the two concepts are similar but in a different context.

• Sorry but you lost me at conduction band. I forgot to say im learning high school physics Mar 25 '17 at 10:00