Atomic theory gr 9 -may 24
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ATOMIC THEORY Lewis
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atomic molecular theory notes May 24
Transcript of Atomic theory gr 9 -may 24
ATOMIC THEORY
Lewis
1700’s1700’s
• In the 1700’s scientist agreed that elements could not be broken down.
• 30 +/- elements identified or known
• Belief that elements could be mixed together to form compounds
• In the 1700’s scientist agreed that elements could not be broken down.
• 30 +/- elements identified or known
• Belief that elements could be mixed together to form compounds
1808 - John Dalton1808 - John Dalton
• Dalton proposed an Atomic Theory to explain chemical reactions. • He envisioned the ATOM.
* smallest particles of an element* smooth solid sphere* no electrical charge
• there was a belief that atoms and molecules were thought to be the same until Dalton.
• Scientists now believed that 2 or more Non-Metalic atoms could be combined to
form compounds.
• Dalton proposed an Atomic Theory to explain chemical reactions. • He envisioned the ATOM.
* smallest particles of an element* smooth solid sphere* no electrical charge
• there was a belief that atoms and molecules were thought to be the same until Dalton.
• Scientists now believed that 2 or more Non-Metalic atoms could be combined to
form compounds.
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1808 - John Dalton Theory1808 - John Dalton Theory
• All matter was made of ATOMS - these were to small to see.
• Each element has its own kind of Atom with its own mass.
• All Atoms of a single type of element are identical.
• Compounds are created when atoms of different elements combine in a specific ratio.
• Atoms can not be created, destroyed, or subdivided during a chemical change
• All matter was made of ATOMS - these were to small to see.
• Each element has its own kind of Atom with its own mass.
• All Atoms of a single type of element are identical.
• Compounds are created when atoms of different elements combine in a specific ratio.
• Atoms can not be created, destroyed, or subdivided during a chemical change
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In the 1800’sIn the 1800’s• until Dalton’s work many scientists believed
that molecules and atoms were the same.
• after Dalton it was accepted that a molecule was the combination of two or more non-metal atoms in combination.
• in 1830 Michael Faraday showed atoms can gain electrical charges. (static electricity)
• until Dalton’s work many scientists believed that molecules and atoms were the same.
• after Dalton it was accepted that a molecule was the combination of two or more non-metal atoms in combination.
• in 1830 Michael Faraday showed atoms can gain electrical charges. (static electricity) QuickTime™ and a
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Michael FaradayMichael Faraday added the following to ATOMIC THEORY
• matter must contain positive (+) and negative (-) charges.
• opposite charges attract & like repel
• atoms combine to form the particles of a compound because of the electrical attraction between the charges atoms ( Ions ).
added the following to ATOMIC THEORY
• matter must contain positive (+) and negative (-) charges.
• opposite charges attract & like repel
• atoms combine to form the particles of a compound because of the electrical attraction between the charges atoms ( Ions ).
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1898 - J.J. Thomson1898 - J.J. Thomson • discovered the presence of smaller particles
than the atom… the negatively charged ELECTRON,
• he proposed than the atom is mostly positively charged matter with small negatively charged electrons scattered randomly throughout.
The Plum Pudding Model ( or the chocolate cookie )
• discovered the presence of smaller particles than the atom… the negatively charged ELECTRON,
• he proposed than the atom is mostly positively charged matter with small negatively charged electrons scattered randomly throughout.
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Thomson’s revisions to Atomic theoryThomson’s revisions to Atomic theory• Atoms contain electrons.
• electrons have a negative charge and a very small mass.
• the rest of the Atom is positively charged.
• electrons can be added and removed. ( ie. Rubbing a balloon against cloth )
• Atoms contain electrons.
• electrons have a negative charge and a very small mass.
• the rest of the Atom is positively charged.
• electrons can be added and removed. ( ie. Rubbing a balloon against cloth )
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Ernest Rutherford - 1911the Canadian connection
Ernest Rutherford - 1911the Canadian connection
While at the University of McGill, Quebec, Rutherford shot alpha particles at gold foil and found that most went straight through.
He reasoned that most of the mass and the positive particles were at the centre of the atom… he called this the nucleus.
While at the University of McGill, Quebec, Rutherford shot alpha particles at gold foil and found that most went straight through.
He reasoned that most of the mass and the positive particles were at the centre of the atom… he called this the nucleus.
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Ernest Rutherford Rutherford amended the Atomic Theory to include the following.
Ernest Rutherford Rutherford amended the Atomic Theory to include the following.
• the Nucleus contains all of the positive charges and most of the mass.
• the Nucleus contains positively charged Protons and uncharged Neutrons.
• Neutrons have some mass, Protons have more.
• the Nucleus is very small.
• Electrons orbit the nucleus like satellites.
• the mass of an electron is 1/1800 of the protons.
• the size of an atom is determined by the size of orbit of electrons.
• there is empty space between the nucleus and the electrons.
• the Nucleus contains all of the positive charges and most of the mass.
• the Nucleus contains positively charged Protons and uncharged Neutrons.
• Neutrons have some mass, Protons have more.
• the Nucleus is very small.
• Electrons orbit the nucleus like satellites.
• the mass of an electron is 1/1800 of the protons.
• the size of an atom is determined by the size of orbit of electrons.
• there is empty space between the nucleus and the electrons.
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• When Rutherford published his findings in 1912, he knew that his version of the ATOMIC THEORY already had errors and would need to be revised.
• When Rutherford published his findings in 1912, he knew that his version of the ATOMIC THEORY already had errors and would need to be revised.
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Modern Atomic Theory
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