Ionisation Energy of Hydrogen (1 Viewer)

[Jase]

Okay so this was in CSSA 2003 trial:

find the ionisation energy for hydrogen - 3 marks.

Do they seriously expect everyone to know what ionisation is and use the E=hcR thing, or is there some kind of super quick way.. mind you they don't provide the energy diagram so you can't just say, well... its obviously 13.6 eV

I doubt most "physics only" people know what ionisation energy is ... that's kinda unfair.

 

[Xayma]

Use the energy of the wavelength of a photon to move it from n=1 to n=∞

 

[smallcattle]

Use the energy of the wavelength of a photon to move it from n=1 to n=∞

can u explain a bit more?? i dont understand this question

 

[Jase]

Ionisation energy is the energy required to remove an electron from the atom. Since Hydrogen only has a proton and an electron, its bassically the binding energy.

Im not quite sure what Xayma means, this is how i think it should be done:

using rydberg's formula, find the energy of an electron dropping from n=1 to n=infinity (it's removed)
so 1/w = R where R is Rydberg's constant and w is wavelength
then using E=hf and c=fw

you get w = ch/E so 1/w = E/ch
hence E/ch = R
E = chR
= 2.18xlargenumber Joules or something i forget
then convert that to eV and it should be 13.6eV

EDIT: Oh yeah i just realised this is exactly what he means by wavelength of a photon..lol

 

[Xayma]

Exactly it would be the energy of the photon emitted (which is calculated from its wavelength) when moving from n=∞ to n=1 or absorbed to move from n=1 to n=∞

 

[jumb]

What topic is this?

 

[Xayma]

From Quanta to Quarks.

 

[jumb]

Oh good. I'm glad I dont understand now.