## Size of nucleus = delta x?

$\Delta p \Delta x\geq \frac{h}{4\pi }$

KNguyen_1I
Posts: 101
Joined: Sat Aug 17, 2019 12:16 am

### Size of nucleus = delta x?

In today's lecture review, why do we consider the size of the nucleus (the 1.7 x 10^-15 or something) as the delta x? I don't conceptually understand why we plug that value in for the uncertainty in position. Are we saying that within that value or less is where the electron could be located? And so if the delta x we plug in is bigger (like how an actual atom model would be) what does that conceptually mean?

John Liang 2I
Posts: 102
Joined: Fri Aug 30, 2019 12:18 am

### Re: Size of nucleus = delta x?

KNguyen_3G wrote:In today's lecture review, why do we consider the size of the nucleus (the 1.7 x 10^-15 or something) as the delta x? I don't conceptually understand why we plug that value in for the uncertainty in position. Are we saying that within that value or less is where the electron could be located? And so if the delta x we plug in is bigger (like how an actual atom model would be) what does that conceptually mean?

Yes! The "faulty" model of the atom that we proved wrong in class is imagining if the electron was stuck directly on top of the nucleus (if the delta x was the size of the nucleus). If the delta x was bigger that would decrease the uncertainty in the electron's momentum and velocity (which is more like the real model of the atom).

Sartaj Bal 1J
Posts: 101
Joined: Thu Jul 25, 2019 12:17 am

### Re: Size of nucleus = delta x?

Usually, in problems like these, it is implied to use the given measurement in the equation. Since the uncertainty in velocity was greater than the speed of light, the model of electrons being in the nucleus is proven as invalid.

LNgo 1G
Posts: 100
Joined: Sat Aug 24, 2019 12:16 am

### Re: Size of nucleus = delta x?

The uncertainty, or delta x value, represents the distance that the electron can be located. If the uncertainty is larger in the case of the example that we did in class, that would mean that the electron would exist outside the nucleus of the atom.