Download - 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 ModelThe Wave-
Particle 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 solid indivisible particles.
* Elements differ in their atom’s size
J. J. Thomson’s Model
• Believed that protons and electrons were mixed together
• Known as the “plum pudding” or
Proposed in 1897
“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
1717
ClCl ChlorineChlorine
35.4535.45
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 asthe 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
foundEnergy 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• 1st- contain maximum 2• 2nd- contain maximum 8• 3rd- contain maximum 18• 4th - contain maximum 32