Scientists And Their Contributions

Question 1

John Dalton

Answer 1

Proposed the first modern atomic model “billiard model”.
Developed the idea of the atomic nature of matter.
Accounted for the Law of Constant Composition in his theory.

Question 2

J.J Thompson

Answer 2

Studied matter in cathode rays.
Added to the atomic theory the idea that atoms had positive and negative parts.

Question 3

Ernest Rutherford

Answer 3

Good Foil experiment.
Discovered the nucleus.
Most of the atom is empty space.
Electrons are flying fixed around the nucleus in an orbit.

Question 4

Max Planck

Answer 4

Stated that the energies of atoms in a heated solid were not continuous. But rather multiples of a smaller amount of energy.

Question 5

Albert Einstein

Answer 5

Used the concept of light consisting of quanta of energy to explain the photoelectric effect.
A quantum of energy is equivalent to a photon.

Question 6

Henrich Hertz

Answer 6

Discovered the photoelectric effect by accident.
Photoelectric effect: When light shining on a metal surface causes the emission of electrons from the metal.

Question 7

Neil’s Bohr

Answer 7

• Concluded that electrons travel in circular orbits in the atom with quantized energy.
• He added electricity to hydrogen gas and used a spectroscope to study the pattern of light it gave off.
• Line Spectrum

Question 8

James Chadwick

Answer 8

• He discovered the neutron, which is found in the nucleus and has no charge.
• He did this by bombarding beryllium atoms with alpha particles, they gave off a beam of particles that was not affected by a magnetic field.

Question 9

De Broglie

Answer 9

• Hypothesized that electrons behaved as standing waves around the nucleus of an atom.
• The wave-like motion of small objects such as electrons is significant.
• Because of their constant motion and electrostatic repulsion, electrons do not move in simple. defined orbits as Bohr suggested

Question 10

Erwin Shrodinger

Answer 10

• Concluded that electron behaviour cannot be exactly described, but only discussed as a wave mechanical question.
• Combined De Broglie’s wave-like motion of particles and Planck/Einstein’s idea of electrons within an atom.
• Schrodinger used mathematical wave functions to determine orbitals: regions in 3-D space where an electron can be found most of the time.

Question 11

Werner Heisenberg

Answer 11

• Stated that there are limits to our ability to know both the location and the momentum of electrons.
• An experiment designed to determine an electrons position will change the electrons momentum.
• An experiment designed to determine an electron momentum will change the electron’s location.

Question 12

Marie Curie

Answer 12

Suggested that atoms could disintegrate.

Question 13

Democritus

Answer 13

Had a philosophical idea that included the term “atomos”

Question 14

Dimitri Mendeleev

Answer 14

Developed the first periodic table of elements

Question 15

Gustav Kirchhoff

Answer 15

Discovered that the blackbodies would radiate different colours of light depending on their temperature and helped to invent the electroscope.