Download Atomic Theory PPT

A Brief History of Atomic
Theory
This Section will focus on Scientists who have had an impact
on the study of the atom.
Ready To Meet Them?
Democritus
Democritus proposed that
matter cannot be broken
down indefinitely.
At some point you end up
with a piece that can’t be
divided.
470-380 B.C.
The smallest piece of
matter he called an atom,
from the Greek word
atomos, which means
“indivisible”.
Next Slide
Democritus’ Model
“Atomos”
John Dalton
John Dalton was a British
chemist. He was the first
modern scientist to propose
the existence of atoms.
He described an atom as an
invisible indestructible, solid
sphere, like a billiard ball.
1766 - 1844
Dalton’s Model
The “Indivisible Sphere”
Sir Joseph “J.J.”
Thomson
J.J. Thomson was a
British physicist who was
the first scientist to
propose the plum pudding
model.
1856 - 1940
He was also the first to
propose the theory of the
negatively charged
electron.
Sir Joseph “J.J.”
Thomson
1856 - 1940
Thomson “plum pudding” model
+
-
Ernest Rutherford
Ernest Rutherford
experiments proved that
atoms are mostly empty
space .
Discovered the nucleus,
which contains positively
charged particles .
1871- 1937
Was the first to suggest that
electrons circle the dense
nucleus.
Ernest Rutherford
1871- 1937
Rutherford’s Model
Nucleus
It has a
+ charge
Electron Negative charge
Niels Bohr
Niels Bohr stated that
electrons move in
different orbits, or
energy levels, around the
nucleus like planets orbit
the sun.
Each energy level is
located a specific
distance from the
nucleus and contains a
certain number of
electrons.
1885 - 1962
Next Slide
Bohr Model
Energy
levels
Current Model
This model is
based upon Bohr’s
model, except that
electrons orbit the
nucleus in random
patterns.
The region where
these particles are
found is referred
to as the electron
cloud.
Next Slide
Determining PEN Numbers
Demitri Mendeleev
Demitri Mendeleev was a
Russian scientist. He was
the first person to make
the periodic table. The
periodic table is a tool to
help organize the
elements.
Mendeleev’s Table
Modern Periodic Table
How to Use the Table
Number of
Protons &
Electrons
Atomic
Number
Chemical
Symbol
6
C
Element
Name
Carbon
12.01115
Atomic Mass = P + E + N
How to find number of Protons
& Electrons
Atomic Number/ number
of Protons/Electrons
6
C
The number of Protons in
atom is also the Atomic
number, so therefore the
Atomic number also
represents the amount of
Protons in the nucleus of
that Atom. In a neutral
Atom Protons = Electrons
CARBON
12.01115
How to Find the Amount
of Neutrons in an Atom
To find the amount of
neutrons in an atom
you have to subtract
the atomic mass from
the atomic number .
16
S
sulfur
32.064
Atomic
Mass
32
Atomic
Number
16
16
Number of
Neutrons
Calculating P, E, N
6
P=
E=
N=
C
Carbon
12.01115
Calculating P, E, N
6
P=6
E=6
N=6
C
Carbon
12.01115
Calculating P, E, N
20
P=
E=
N=
Ca
Calcium
40.08
Calculating P, E, N
20
P = 20
E = 20
N = 20
Ca
Calcium
40.08
Calculating P, E, N
26
P=
E=
N=
Fe
Iron
55.847
Calculating P, E, N
26
P = 26
E = 26
N = 30
Fe
Iron
55.847
Complete Worksheet
Complete Worksheet