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Thomsons Plum Pudding Model of the Atom - Atoms Video Lecture - Class 12

FAQs on Thomsons Plum Pudding Model of the Atom - Atoms Video Lecture - Class 12

1. What is Thomson's Plum Pudding Model of the Atom?

Ans. Thomson's Plum Pudding Model of the Atom, proposed by J.J. Thomson, suggests that an atom consists of a positively charged sphere with negatively charged electrons embedded in it, resembling plums in a pudding. This model implies that atoms are uniform and do not have a distinct nucleus.

2. Who proposed the Plum Pudding Model of the Atom?

Ans. The Plum Pudding Model of the Atom was proposed by J.J. Thomson, a British physicist, in 1904. This model was developed based on his experiments with cathode rays and the discovery of negatively charged particles called electrons.

3. How does the Plum Pudding Model explain the structure of an atom?

Ans. According to the Plum Pudding Model, an atom consists of a positively charged sphere, representing the atom's mass, with negatively charged electrons embedded within it. The positive charge of the sphere balances the negative charge of the electrons, resulting in an overall neutral atom. This model suggests that atoms are uniform and have no distinct nucleus.

4. What were the limitations of Thomson's Plum Pudding Model?

Ans. Thomson's Plum Pudding Model had several limitations. Firstly, it failed to explain the stability of the atom since the negatively charged electrons should be attracted to the positively charged sphere and collapse into it. Secondly, it did not account for the presence of a central, heavy nucleus in the atom. Lastly, it could not explain the results of later experiments, such as the scattering of alpha particles by Rutherford, which led to the discovery of the atomic nucleus.

5. How was Thomson's Plum Pudding Model disproven?

Ans. Thomson's Plum Pudding Model was disproven by the famous gold foil experiment conducted by Ernest Rutherford in 1911. In this experiment, Rutherford bombarded a thin gold foil with alpha particles and observed their scattering patterns. The unexpected large-angle deflections of some alpha particles indicated the presence of a concentrated positive charge at the center of the atom, later known as the atomic nucleus. This discovery disproved Thomson's model and paved the way for the development of the nuclear model of the atom.

Text Transcript from Video

So the word atom means uncuttable
so the Greeks were thinking of it as a tiny hard
sphere
Phil: that's right
Derek: and even up until the eighteen
hundred's that was the idea of an atom, the
smallest piece of matter, a tiny hard sphere
but then we find out that that's not quite
right
not quite
there were experiments in the eighteen hundreds
that discovered the electron, JJ Thomson's
experiments
really worked out the electron was
smaller than an atom, about 1000
times smaller than a hydrogen atom
and it was in all atoms
that's right, not just hydrogen
whatever material he did his experiments on
he found there was electrons in them
there are electrons in an all atoms
so I guess when you find something smaller than an atom
you need to propose a new model for the atom
that actually has something smaller in it some
substructure
Phil: that's right so something
like this
this is our model of the atom
Phil: This is our model of the atom -
in his day, it was known as the plum pudding
model but uh... here we have
cherry tart
Phil: cherry tart, ok so
but the idea being that we have an overall atom
usually pictured as spherical rather than 2D but
uh... but imbedded within it
and this is the important part
there are negative electrons represented by
cherries and they can come out
the overall atom is neutral, so
that means that pudding part must be positive
Derek: now how would you get one of these
electrons
out of our pudding here
so electrons are negatively charged so we'll need
to put something very positive which attracts
electrons, a high voltage
Derek: and that would have
the effect of say like
plucking a cherry out of the pudding
that's pretty much it
yeah you could do it kind of like that
so we're simulating
what it would be like
to put a positive charge up here.
Phil: that's right, that's right
Derek: pulling the electrons out of the atom
that's quite a
delicious
Phil: Yeah!
well that is the most delicious model of the atom,
I've gotta say
so shall we uh split the atom?
why don't you go ahead
Phil: you want me to do it?
Derek: yes
Who knows what could happen,
a whole bunch of energy could be released.
Phil: Yeah
one, two, three...

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Mar 07, 2025 Last updated

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