John Dalton developed the first modern atomic theory which stated that elements are made of extremely small indivisible particles called atoms. Atoms of a given element are identical but differ from atoms of other elements. Atoms combine in simple whole number ratios to form compounds. Niels Bohr contributed the Bohr model of the atom which depicted electrons traveling in discrete orbits around the nucleus. He also developed the shell model which explained an element's chemical properties based on its outermost electrons. Bohr received the 1922 Nobel Prize in Physics for his investigations into atomic structure and radiation. He played an important role in the development of quantum mechanics and nuclear physics.

1. Dalton and Bohr
Done by:-
Chintan
Dev
Manav

2. Mr. John Dalton
intro.
• John Dalton (6 September 1766 – 27 July
1844) was an
English chemist, meteorologist and physicist.
He is best known for his pioneering work in
the development of modern atomic theory,
and his research into colour
blindness (sometimes referred to as
Daltonism, in his honour).

3. John Dalton

4. Dalton’s atomic theory….
• Elements are made of extremely small particles
called atoms.
• Atoms of a given element are identical in size, mass,
and other properties; atoms of different elements
differ in size, mass, and other properties.
• Atoms cannot be subdivided, created, or destroyed.
• Atoms of different elements combine in simple whole-
number ratios to form chemical compounds.
• In chemical reactions, atoms are combined, separated,
or rearranged.

5. Dalton’s atomic model

6. Some of his achievements
• He was president of the Lit & Phil from 1817 until his
death, contributing 116 memoirs.
• In 1800, Dalton became a secretary of the
Manchester Literary and Philosophical Society, and in
the following year he orally presented an important
series of papers, entitled "Experimental Essays" on
the constitution of mixed gases

7. We thank john Dalton for his
beautiful work…….

8. Mr. Niels Bohr
intro.
• Niels Henrik David Bohr (7 October 1885 – 18
November 1962)was a Danish physicist who
made foundational contributions to
understanding atomic structure and quantum
mechanics, for which he received the Nobel
Prize in Physics in 1922.

9. Niels Bohr

10. Contribution to physics and chemistry
• The Bohr model of the atom, the theory that electrons travel
in discrete orbits around the atom's nucleus.
• The shell model of the atom, where the chemical properties
of an element are determined by the electrons in the
outermost orbit.
• The correspondence principle, the basic tool of Old quantum
theory.
• The liquid drop model of the atomic nucleus.
• Much work on the Copenhagen interpretation of quantum
mechanics.
• Identified the isotope of uranium that was responsible for
slow-neutron fission – 235U.

11. Bohr model of atom

12. Niels’ Achievements
• In 1922, Bohr was awarded the Nobel Prize
in physics "for his services in the investigation of the
structure of atoms and of the radiation emanating
from them.
• Among the international community of nuclear
physicists, Bohr came to play the role of convener of
discussion groups and lectures, as well as being a
mentor and an advisor.

13. We thank niel bohr for for his
tremendous contribution towards
physics and chemistry

14. Thank you and have a very nice
day………..