Development of the Atomic Theory
Democritus – 460 BC
ABOUT:
460 BC - Greek philosopher proposes the existence of the atom
He pounded materials until he made them into smaller and smaller parts
He called them atoma which is Greek for “indivisible”.
HIS THEORY:
Are small hard particles
Are made of a single material formed into different shapes and sizes
Are always moving, and they form different materials by joining together
John Dalton – 1803
ABOUT:
1803 - British chemist; elements combine in specific
proportions to form compounds
HIS THEORY:
•All substances made of atoms, cannot be created/divided/destroyed.
•Atoms join with other atoms to make new substances.
•Atoms of the same element are exactly alike, and atoms of
different elements are different in mass and size.
Model
Drawing:
J.J. Thomson– 1897
ABOUT:
1897 - English chemist and physicist; discovered 1st subatomic particles
HIS THEORY:
•Atoms contain negatively charged particles called electrons
and positively charged matter.
•Created a model to describe the atom as a sphere
filled with positive matter with negative particles mixed in
•Referred to it as the plum pudding model
Model
Drawing:
Ernest Rutherford– 1912
ABOUT:
1912 - New Zealand physicist discovered the nucleus
HIS THEORY:
Small, dense, positively charged particle present in
nucleus called a proton
Electrons travel around the nucleus, but their
exact places cannot be described.
Model
Drawing:
Development of the Atomic Theory
Niels Bohr – 1913
ABOUT:
1913 - Danish physicist; discovered energy levels
HIS THEORY:
Electrons travel around the nucleus in definite paths
and fixed distances.
Electrons can jump from one level to a path in another level.
Model
Drawing:
Erwin Shrodinger – 1924
ABOUT:
1924 - Austrian physicist; developed the electron cloud model
HIS THEORY:
The exact path of electrons cannot be predicted.
The region referred to as the electron cloud, is an area
where electrons can likely be found.
Model
Drawing:
James Chadwick– 1932
ABOUT:
1932 - English physicist; discovered neutrons
HIS THEORY:
Neutrons have no electrical charge.
Neutrons have a mass nearly equal to the mass of a proton.
Unit of measurement for subatomic particles is the atomic mass unit (amu).
Modern Theory of the Atom
•Atoms are composed of three main subatomic particles: the electron, proton, and neutron.
•Most of the mass of the atom is concentrated in the nucleus of the atom.
•The protons and neutrons are located within the nucleus, while the electrons exist outside of the
nucleus.
•In stable atoms, the number of protons is equal to the number of electrons.
•The type of atom is determined by the number of protons it has.
•The number of protons in an atom is equal to the atomic number.
The sum of the number of protons and neutrons in a particular atom is called the atomic mass.
Valence electrons are the outermost electrons.
Development of the Atomic Theory
________________– 460 BC
ABOUT:
460 BC - Greek philosopher proposes the existence of the ___________
He pounded materials until he made them into smaller and smaller parts
He called them _____________ which is Greek for “______________”.
HIS THEORY:
Are ________________________
Are made of a ____________________________formed into different shapes and sizes
Are ____________________, and they form _______________________by joining together
____________________________– 1803
ABOUT:
1803 - British chemist; elements combine ________________________
to form ___________________
HIS THEORY:
•All substances __________________, cannot be _____________________.
Model
•Atoms join with other atoms to make _________________________.
Drawing:
•Atoms of the ______________________ are exactly alike, and atoms of
___________________________________are different in mass and size.
_____________________________– 1897
ABOUT:
1897 - English chemist and physicist; discovered
________________________________________
HIS THEORY:
•Atoms contain ______________________ particles called ___________
and _______________________________.
•Created a model to describe the atom as a sphere
filled with positive matter with negative particles mixed in
•Referred to it as the ________________/______________ model
Model
Drawing:
______________________________– 1912
ABOUT:
1912 - New Zealand physicist; _____________________________
HIS THEORY:
Small, dense, ___________________________ particle present in
________________ called a _____________________
_______________________ travel around the ____________, but
their exact places cannot be described.
Model
Drawing:
Development of the Atomic Theory
________________________– 1913
ABOUT:
1913 - Danish physicist; discovered ______________ (orbitals/shells)
HIS THEORY:
_________________ travel around the nucleus in ____________
Model
and _______________________.
Drawing:
Electrons can _________from one level to a path in another level.
Erwin Shrodinger – 1924
ABOUT:
1924 - Austrian physicist; developed the ______________________
HIS THEORY:
The exact path of electrons ______________________________.
The region referred to as the _____________________, is an area
where electrons can likely be found.
Model
Drawing:
James Chadwick– 1932
ABOUT:
1932 - English physicist; discovered ____________________
HIS THEORY:
_______________________________ have no electrical charge.
Neutrons have a mass _____________________ to the mass of a __________________.
Unit of measurement for subatomic particles is the ____________________ (amu).
Modern Theory of the Atom
•Atoms are composed of three main subatomic particles: the ________, ___________, ________.
•Most of the mass of the atom is concentrated in the __________________ of the atom.
•The __________ and ______________ are located within the nucleus, while the ______________
exist outside of the nucleus.
•In stable atoms, the number and charge of ______ is equal to the number and charge of _______.
•The type of atom (IDENTITY) is determined by the number of __________________ it has.
•The number of ______________________ in an atom is equal to the _________________.
•The sum of the number of ___________ & ________in a particular atom is called the
__________.
•________________are the outermost electrons.
Development of the Atomic Theory
Democritus – 460 BC
ABOUT:
HIS THEORY:
John Dalton – 1803
ABOUT:
HIS THEORY:
Model
Drawing:
J.J. Thomson– 1897
ABOUT:
HIS THEORY:
Model
Drawing:
Ernest Rutherford– 1912
ABOUT:
HIS THEORY:
Model
Drawing:
Development of the Atomic Theory
Niels Bohr – 1913
ABOUT:
HIS THEORY:
Model
Drawing:
Erwin Shrodinger – 1924
ABOUT:
HIS THEORY:
Model
Drawing:
James Chadwick– 1932
ABOUT:
HIS THEORY:
Modern Theory of the Atom