L1 - Thomson's Atomic Model - Structure of Atom, Class 9, Science Video Lecture

in this module you will learn about
Thompson's atomic model other charged
particles ranged in any particular
manner are the charged particles spread
throughout the atom or are they
concentrated in one place to answer
these questions let's go back in time
Downton's atomic theory stated that an
atom was indivisible and indestructible
however in 1886 Goldstein came upon
positively charged radiations in a gas
discharge which he termed as annal rays
these radiations led to the discovery of
the proton the mass of a proton was
about 2,000 times that of an electron
and it carried a positive charge around
the year 1900 JJ Thompson conducted
experiments on the beams of particles
inside a glass tube called a cathode ray
tube he found that the particles were
attracted to the positive terminal of
the tube Thomson concluded that the
particles must be negatively charged and
called these particles electrons an
electron has a negligible mass and has a
charge of minus 1 these discoveries mean
that scientists believe that an atom was
divisible and made up of electrons and
protons what they didn't know at the
time was how these electrons and protons
were arranged within an atom
then try to understand this arrangement
through various experiments JJ Thompson
was the first to put forward a model to
explain the structure of an atom in his
model Thompson compared an atom to a
Christmas pudding the electrons were
like the raisins in the pudding and the
pudding itself was like the positively
charged particles this can also be
explained through the example of a
watermelon
the positive charge in the atom is
spread all over like the red fleshy part
of the watermelon while the electrons
are embedded into the atoms like the
seeds of the watermelon the oppositely
charged particles are held together by
electrical force of attraction
Thompson concluded that an atom consists
of a positively charged sphere with
electrons set within the sphere an atom
to clean neutral as the positive and
negative charges within it are equal as
per Thompson's conclusion the electrons
were embedded in a sphere of positive
charge this conclusion however was
incorrect
Thompson asserted at the positive charge
spread through the atom held the
negatively charged electrons due to
electrical forces this assertion failed
to explain many experimental
observations in this module you have
learnt that atoms are made of charged
particles according to Thomson's model
an atom is a positively charged sphere
with electrons set within it an atom is
electrically neutral shortcomings of
Thomson's model are his incorrect
assumptions electrons are embedded in
positive charged positive charge in the
atom holds the negatively charged
electrons