ppt lakshmi
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o All matter is made up of small particles called atoms.
o Atom is the smallest particle which can engage in a chemical reaction.
o All the atoms of an element have the same properties.
o Atoms of different elements have different characters.
o atoms can neither be created nor destroyed.
o Atoms are indivisivble.
POSTULATES OF DALTON ON AN ATOM
o Electrons carrying negative
charge.
o Mass of an electron is
1/1837 of themes of the
smallest atom - hydrogen
DISCHARGE TUBE EXPERIMENT
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GOLD FOIL EXPERIMENT
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gold foil
beam ofalpha particles
undeflected particles
deflected particle
· Atom has a central part called nucleus.· Nucleus has positive charge· The mass of atom is concentrated in the nucleus.
· Electrons are distributed in the space around the
nucleus.
BOHR MODEL In Neil’s Bohr atom
model each of the orbit is
a specific energy level.
The energy levels 1, 2, 3,
4 and 5 are represented
by the letters K, L, M, N,
and O respectively.
These energy levels are
known as shells
Number of Protons in an atom is the atomic
number of the elements.
Mass Number is the total number of protons
and neutrons.
The maximum number of electrons that a shell
can contain can found out using the formula‘2 ’
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