Could someone please explain the exclusion and uncertainty principle? (2 Viewers)

[mercho]

Hey everyone,
Could someone please explain the exclusion and uncertainty principle in lame terms, as i have read about them but still dont really understand...
thanks guys

 

[richz]

exclusion - no two electrons can have the same set of principle quantum no. helped explain the periodic table and the shells of atoms

uncertainty - it is impossible to accurately measure the momentum and position of a particle at the same time. so everything changed from a definite exact view to a probablity satistical view

i hope this is rite, off the top of my head

 

[mercho]

thanks mate,
another quick question (as i have a list of them) how has the predictive capabilities affected the world over the past 80 years compared to all history. I know generally what it is talking about but i cant put it into suitable words.
Thanks for any help in advance

 

[richz]

lol, no idea doesnt sound lke physics lol but then again the physics course isnt physics

Where did u get the question from?? sounds like a gay question.

 

[mercho]

question is one set from class, this is how it looks:
Describle the exclusion principle.
How has this predictive capability affected the world over the lat 80yrs compared to all previous history.
How has this principle affected our understanding of the atomic theory.

Thanks again!

 

[wanton-wonton]

but then again the physics course isnt physics

Yes it is. What else could it be?

 

[who_loves_maths]

Originally Posted by xrtzx
exclusion - no two electrons can have the same set of principle quantum no. helped explain the periodic table and the shells of atoms.

more accurately:

It is a principle that states that no two (or more) fermions can occupy the same quantum state.

the case for the electron in an atom is a special case of the Pauli Exclusion Principle.


Moreover, unlike what xrtzx has said, two electrons CAN have the same set of principal quantum no. - since the principal quantum no. is merely the integer 'n' which corresponds to orbitals or energy levels around the nucleus of an atom.
two electrons can indeed occupy the same orbital around the nucleus of an atom - you would know this from Chemistry where you learnt that different 'shells' can hold different numbers of electrons > 1, in each shell.

But what the electrons can't do, and i think this is what xrtzx was trying to say, is to share the same quantum state - which contains more quantum numbers (eg. magnetic moment, spin, etc...) than simply the one principal quantum number.

the best example of this is the Helium atom:
two electrons orbit the nucleus and BOTH can occupy the lowest energy (ground) state {you should know this also from Chemistry} around the nucleus - both corresponding to the principal quantum number n=1.
BUT, this is only possible because the two electrons have different (opposite) spins - which means their overall quantum states are different to each other, even though they share the same principal quantum number.
hence, Pauli's Exclusion Principle is obeyed in this way for the Helium atom.


the concept of electron spin follows on as a necessary part of the description of fermions because it is a logical consequence of Pauli's Exclusion Principle (and other phenomenon too) and is need to differentiate between two or more fermions. {the concept of spin was introduced in 1925 - only one year after Pauli's proposition of his exclusion principle.}


in terms of the consequences and contributions of the Exclusion Principle to Atomic Theory:

1) the explanation of the regularities within the Periodic Table and why different elements are made up of atoms that differ chemically from each other.

2) a new physical 'picture' of an atom with orbital, as opposed to circular shells, and more importantly, sub-orbitals within a main orbital (eg. the p's, d's, f's, etc...)

3) the explanation of energy levels within the nucleus of an atom itself - providing distinction between each individual neutron and proton within a nucleus. {remember that neutrons and protons are fermions also, thus must obey the law.}
this also goes hand in hand with George Gamow's Liquid Drop model of the nucleus of an atom.


generally speaking, along with QED (Quantum Electrodynamics), the Exclusion Principle is responsible (as a theoretical explanation) for almost all of the discipline of Chemistry.


hope that helps to clear some things up mercho