PANDITA RAMABAI- Indian political thought GENDER.pptx
Atomic theory
1.
2. Atomic Theory
• Democritus (440 BCE)-
realized that if you continued
to cut something, eventually
you would end up with
something that couldn’t be
cut anymore, “atomos” –
meaning not able to divide
• Atoms smallest particle
that an element can be
divided & still be the same
substance
• All matter is made of atoms
3.
4. John Dalton (1803)
• realized that atoms combine
in very specific proportions
(ratios) based on mass
• all substances are made of
atoms and they cannot be
created, divided or destroyed
(made of a single substance)
• All atoms of the same
element are exactly alike and
different from other elements,
(unique)
• Atoms join with other atoms
to form new substance
5.
6. J. J. Thomson (1897)
• discovered that there were
small particles inside the
atom, meaning that atoms
can be divided into smaller
substances
• Electrons – negatively
charged particles attracted to
positively charged particles
• Plum pudding model –
electrons are mixed
throughout the atom, soft
blobs of matter
7.
8. Ernest Rutherford (1909)
• Discovered that an
atom contains a
nucleus with
positively charged
particles and that the
electrons must be
“floating” around the
nucleus
• Most of an atom is
empty space
9.
10.
11. Niels Bohr (1913)
• Proposed that electron
moved around the
nucleus in energy levels
(shells), but no electrons
between the energy level
(think ladder)
• Electrons can jump from
one level to another
• Travel in a definite path
12.
13. Modern Atomic Theory
• Erwin Shrodinger &
Werner Heisenberg
• Electrons have no
predictable pattern
and move in a region
where electrons are
likely to be found
called the electron
cloud
14.
15.
16. Atoms
• All atoms have a nucleus
– protons (+),
– neutrons (no charge)
– electrons (-)
• Same number of protons and electrons an
atom has no charge
• More protons (+) than electrons (-) the atom
has a positive ion form (more positives than negatives)
• More electrons (-) than protons (+) a negative
ion is formed (more negatives than positives)
17. • 117 different elements that are unique and
all things known to exist come from a
combination of these elements in specific
mass ratios
• Simplest atom is made of one proton, and
1 electron – hydrogen (has no neutrons)
18. • All additional element will have protons,
neutrons and electrons
• The atomic number of an element is
determined by the number of protons,
– 1 is hydrogen, 6 is carbon, hydrogen has 1
proton, carbon has 6 protons (you cannot
change the number of protons)
• To find neutrons take the mass number
(rounded) and subtract the protons.
19. Isotopes
• Isotopes have the same number of protons but
additional neutrons which causes the atomic
mass to be different
• Isotopes can be stable (maintain their structure)
and unstable (fall apart over time)
• Unstable isotopes are radioactive and will decay
over time giving off particles and energy
(radioactive)
20. • Mass number
determines the
isotope, the number
of protons and
neutrons added
together
• Most elements have
isotopes
• All isotopes of an
element have the
exact properties of
the element
21. Forces in
atoms
• Gravitational force –
pulls objects toward
each other—depends on
mass and distances
between the objects—
very small force in
atoms
• Electromagnetic force
–– proton (+) and
electrons (-) have strong
attraction which keeps
the electrons in motion
around the nucleus of
22. • Strong force – force
which keeps protons
from flying apart due
to close distance
between protons and
neutrons
• Weak force – relevant
to radioactive atoms-
allows neutrons to
change into proton
and electron
