History of the Atomic Model
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Transcript History of the Atomic Model
Instructional Objective:
1.Learn the atomic models
2.Learn the atomic structure and elements.
History of the Atomic Model
The Greek
Model
Dalton’s
Model
Thomson’s
Model
Rutherfords
Model
Bohr’s Model
The WaveParticle
Model
The Greek Model
• Proposed around 400
B.C. By the Greek
Philosopher Democrats
• Called them “Atomos”, in
Greek means can’t be
divided or destroyed.
John Dalton’s
Model
Proposed the
Atomic Theory
in 1803
All atoms are
made up of
* Elements
solid indivisible differ in their
particles.
atom’s size
J. J. Thomson’s Model
Proposed in 1897
• Believed that
protons and
electrons were
mixed together
• Known as the
“plum pudding”
or
“raisin bread”model
Ernest Rutherford’s Model
• Proposed in 1907
after discovering
atom’s nucleus
• Electrons move
around a central
nucleus
containing protons.
.
Niels Bohr’s Model
• Electrons move in
energy levels
around a central
nucleus
• Electrons can only
be in these
energy levels.
Particle-Wave Model
• James
Chadwick
discovers
neutron in
1935.
• Electrons are
most likely found in energy levels
What is an Atom?
*The smallest unit of a matter is known as
an atom
What is an element?
• An element is made up of only one kind
of atom.
What is a molecules ?
• Is the smallest unit of a compound
What is a substance?
• any element or compound
Structure of an atom
• An atom is made up of a nucleus that
contain protons and neutrons.
• And an outer orbit that contain
electrons.
-Protons are always positive in charge
-Electrons are negative in charge
-Neutrons are neutral or without any
charge
Characteristics of an Atom
• Atom itself has no charge because
protons are always equal to
electrons.
• Ex: Sodium –Protons are 11
--Electrons are also 11
( Positive and negative will cancel each
other)
Properties of subatomic particles
• Protons, electrons and neutrons are the
subatomic particles
• Protons are always positive in charge
• Electrons are negative in charge
• Neutrons are neutral or with out any charge
Difference between atomic mass
and Atomic number
• Atomic mass: is the total
number of protons and
neutrons in the nucleus.
• Atomic number: Is the total
number of protons
Element Block from periodic table
• 17 ---- atomic number Cl
---- Symbol
Chlorine –Name
35.45 --- atomic mass
or
mass number
17
Cl
Chlorine
35.45
Other Symbols to remember
p+ →Proton(always positive charge)
e- → electron (always negative in charge)
N0 → Neutrons(zero charge)
<→Less than
> →greater than
+ → and or plus
→ → yield
(s) → solid
(l) → Liquid
(g) → gas
ISOTOPES.
• Atoms of the same element that have
different number of Neutrons.
• Ex: The most common isotope of hydrogen.
-Hydrogen has no neutrons at all(1proton)
-Deuterium, with one neutron.
(1proton+1neutron)
- Tritium, with two neutrons.(1proton+2 neutrons)
Isotopes can be written as
the part of a chemical symbol
• Ex: 15 7N or Nitrogen – 15 ( 15 is the
mass number and 7 is the atomic
number)
• Ex: 3517Cl or Chlorine -35( 35 is the
mass number and 17 is the atomic
number)
• Close to the atomic mass, abundant is
the element in that Isotope.
How are electrons arranged in an atom
Electron Cloud
• The area in an atom where electrons are
found
Energy levels
• Is the place in the electron cloud
• Are in different distance from nucleus
• The closest to nucleus –less and weak
• Far away from nucleus –more and more
powerful
The energy levels
st
•1 -
contain maximum 2
nd
• 2 - contain maximum 8
rd
• 3 - contain maximum 18
th
• 4 - contain maximum 32
Electron Configurations
* Is the arrangement of electrons
in the orbitals of an atom.
Electron configuration
•S orbit- 2 electrons
•P orbit-6 electrons
•D orbit-10 electrons
•F orbit – 14 electrons