The ionisation energy of gold is 890.1 kJ/mol. Is light with a wavelength of 225 nm capable of ionising a gold atom ?

1 Answer
Feb 28, 2015

No it is not.

Ionisation energy refers to:

Au_((g))rarrAu_((g))^++e

1 mole requires 890.1"kJ" =8.901xx10^5"J"

1 atom requires (8.901xx10^5)/(6.02xx10^(23))"J"

=1.478xx10^(-18)"J"

To find the energy of the photon we use:

E=hf

To get the frequency of the photon we use :

c=flambda

c is the speed of light =3xx10^(8)"m/s"

So f=c/lambda=(3xx10^8)/(225xx10^(-9)

f=1.333xx10^(15)s^(-1)

So E=6.63xx10^(-34)xx1.333xx10^(15)"J"

E=8.84xx10^(-19)"J"

So you can see that this falls short of the energy required to ionise the gold atom as it is less than 1.487xx10^(-18)"J".