DAILY QUESTION

September 29, 2008

1. Who’s atomic theory is considered the foundation for the modern atomic theory?

Agenda 9/29/08

• Daily Question

• Chapter 4 - Introduction

Assignments: 1. No Assignments Tonight.

Atomic Theory Timeline~ Year~ Scientist~ Contribution

500 BC 1935

1800

Atomic Theory Timeline~ Year~ Scientist~ Contribution

500 BC 1935

•Democritus: In 4th century BCE (460 BC), he suggested that the universe was made of invisible units called atoms. The word atom is derived from the Greek word meaning “unable to be divided.”

•John Dalton: In 1808 proposed the atomic theory. According to Dalton, all atoms of a given element were exactly the same and the atoms could join to form compounds.

Dmitry Medeleyev – In 1871, he revealed the basic importance of atomic weights and of nuclear structure.

•Sir J.J. Thomson – In 1897, the English physicist explained the nature of the electron.

1800

•Sir Ernest Rutherford – In 1909, he constructed the first nuclear model of the atom, a cornerstone of present-day physics. In 1919, he proved the nucleus could be breached

•Niels Bohr: In 1913, he proposed a model of the atom with electrons orbiting the nucleus similar to the planets revolving around the sun. The orbits of electrons depend on their energy, and electrons can jump from one energy level to another; and energy travels in

discrete quantities.

•James Chadwick and E.S. Bieler: They proposed in 1921 that a strong force held the nucleus together.•In 1932, Chadwick discovered the neutron, a particle with no

electrical charge.

•Louis de Broglie: He proposed in 1924 that electrons could behave as waves under some conditions, a finding that helped scientists understand that the atom didn't behave like the solar system because electrons do not move in regular orbits.

•Erwin Schrodinger: Building on de Broglie's idea that electrons act like waves in some situations, he developed the basic equation of quantum

mechanics in 1926. •Werner Heisenberg: In 1927 he proposed that it is impossible to know the position and velocity of an electron at the same time; this concept is called the

uncertainty principle.

Max Born: Working with Heisenberg in 1927, Born modified Schrodinger's equation of quantum mechanics. His idea helped scientists develop the model of an atom with a nucleus surrounded by electrons at different locations when they are

in different energy states.

Developing the Atomic Theory

• Democritus: In 4th century BCE (460 BC), he suggested that the universe was made of invisible units called atoms. The word atom is derived from the Greek word meaning “unable to be divided.”

• John Dalton: In 1808 proposed the atomic theory. According to Dalton, all atoms of a given element were exactly the same and the atoms could join to form compounds.

Developing the Atomic Theory

• Dmitry Medeleyev – In 1871, he revealed the basic importance of atomic weights and of nuclear structure.

• Sir J.J. Thomson – In 1897, the English physicist explained the nature of the electron.

• Sir Ernest Rutherford – In 1909, he constructed the first nuclear model of the atom, a cornerstone of present-day physics.

Developing the Atomic Theory

• Niels Bohr: In 1913, he proposed a model of the atom with electrons orbiting the nucleus similar to the planets revolving around the sun. The orbits of electrons depend on their energy, and electrons can jump from one energy level to another; and energy travels in discrete quantities.

• James Chadwick and E.S. Bieler: They proposed in 1921 that a strong force held the nucleus together.

• Louis de Broglie: He proposed in 1924 that electrons could behave as waves under some conditions, a finding that helped scientists understand that the atom didn't behave like the solar system because electrons do not move in regular orbits.

Developing the Atomic Theory

• Erwin Schrodinger: Building on de Broglie's idea that electrons act like waves in some situations, he developed the basic equation of quantum mechanics in 1926.

• Werner Heisenberg: In 1927 he proposed that it is impossible to know the position and velocity of an electron at the same time; this concept is called the uncertainty principle.

• Max Born: Working with Heisenberg in 1927, Born modified Schrodinger's equation of quantum mechanics. His idea helped scientists develop the model of an atom with a nucleus surrounded by electrons at different locations when they are in different energy states.

Atoms (page 104-105)

• The smallest part of an element that still has the element’s properties

• Combine to make molecules – Examples: H2O

• Whether 1 molecule or billions, they are always the same: 2 hydrogen to 1 oxygen

What’s in an Atom? (page 106)

Subatomic particles

Proton Neutron Electron

Positive ChargeNegative ChargeNo ChargeFound in NucleusFound in NucleusFound surrounding NucleusVery little massSame mass as a protonSame mass as a neutronSame size as a protonSame size as a neutronVery small size