# Are electrons included in mass defect Q's (1 Viewer)

Title

#### Mr_Kap

##### Well-Known Member
shit. I have to learn mass defect ---> thx for making this post to remind me. If i find out in the next half and hour i'll answer here if no-one else has

are they?

#### pikachu975

##### Premium Member
are they?
It depends what info they give. Mass defect is difference in mass between the constituents of a nucleus and the nucleus itself, so if they give you atomic mass then you have to minus mass of electrons because you want nuclear mass.

Exp

#### blaqdave

##### New Member
yes they are used because the mass defect is measuring only the lack of binding energy. Also the actual atomic mass includes electrons so the answer for your question will be yes.

Exp

#### AhaExperience

##### New Member
I know the guy who set the question on this elective two years in a row...

Mass defect questions will always and only be based on the mass of the nucleus - sorry to earlier responders - so if you are given the mass of Helium-3 nucleus as 3.0160293 amu and the mass of a proton as 1.00727647 amu and the mass of a neutron as 1.008664 amu, then the mass defect is the difference between the mass of the He-3 nucleus and the masses of two protons and two neutrons i.e. 3.0160293 - (2 x 1.00727647 + 1.008664) = -0.007188 amu. Please note that the total mass of the individual protons and neutrons is higher than the mass of the He-3. This difference is due to the binding energy that is needed to hold the He-3 nucleus together.