Download 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