models of the atom ppt

1. Made by = Saloni Rawat
Class = IX – C
School=Grace Academy

2. J.J Thomson (1856-1940) researched the
idea that atoms might be made from a
combination of particles .
Thomson used cathode rays tubes to
produce streams of negatively charged
particles ( laser named electrons).
Because Thomson knew that atoms have
no overall charge , he reasoned that atoms
must contain ‘+’ charges.
Thomson’s model is commonly referred to
as the ‘plum pudding model’.

4. Most of the positive particles went right to the foil
,however , about 1 in 10,000 positive particles
bounced back .
These particles had been deflected by something very
massive and positively charged .
Rutherford has discovered the nucleus – the centre of
the atom .
Rutherford calculated that the size of the nucleus
compared to the rest of the atom was like the size of
the single green plea compared to an entire football
field .
The nucleus is a tiny positively charged part of an
atom that contain most of the atom’s mass .

6. Bohr transformed the model of the atom into one that is
commonly used today .
His model shows how electrons are arranged in different
elements .
Bohr suggested that electrons surround the nucleus in
specific energy levels called ‘shells’.
He discovered that electrons jump between these shells by
gaining or loosing energy .
Each shell can only contain a specific number of electrons .
The first shell can contain a maximum of 2 electrons .
The second and third shell can contain a maximum of 8
electrons each .

8. Here I have came to the end of the presentation on
the topic ‘ models of atom ‘, it was a pleasant
experience while working on this presentation .I
tried my best to include all the necessary points that
are required . I really enjoyed each and every bit of
work I have put in this presentation , thankyou .