Scientists

Question 1

Democritus

Answer 1

matter consisted of indivisible particles called atoms.

Question 2

Dalton

Answer 2

“atomic theory” of atoms. He perceived atoms to be solid little spheres.

Question 3

Arrhenius

Answer 3

discovered the electrical nature of chemical solutions.

Question 4

Faraday

Answer 4

experimented with electricity running through solutions. Discovered matter had electrical properties.

Question 5

Kirchhoff

Answer 5

electrical circuits, spectroscopy (emission/absorption line spectra), and the emission of blackbody radiation by heated objects.

Question 6

Mendeleev

Answer 6

determines there is periodicity of physical and chemical properties of elements in the periodic table.

Question 7

Crookes

Answer 7

“vacuum tube” called Crookes tube. He discovered that rays with a negative charge flowed from the cathode to the anode in gas discharge tubes. These rays are referred to as cathode rays.

Question 8

Goldstein

Answer 8

discovered that rays with a positive charge flowed from the anode to the cathode in gas discharge tubes. These are referred to as canal rays.

Question 9

Röentgen

Answer 9

discovered X-rays and that they had no charge.

Question 10

Bequerel

Answer 10

discovered radioactivity studying uranium salt.

Question 11

Thomson

Answer 11

discovered electrons. He determined the charge/mass ratio of the electron. Plum Pudding Model. He did quantitative studies of cathode rays.

Question 12

Planck

Answer 12

proposed that radiant energy is emitted/absorbed in discrete units called quanta. E = h (h = Planck’s constant = 6.626x10-34 J*s) (λ= frequency)

Question 13

Einstein

Answer 13

proposed that light or free radiant energy dissociated from all matter was particulate. Light is made of particles, each of which carries a definite amount of energy (quantum). A photon is a quantum of light energy.

Question 14

Millikan

Answer 14

determined the charge of the electron via the charged oil drop experiment. Mass of an electron = 0.00055 u.

Question 15

Rutherford

Answer 15

discovered the nucleus conducting the “Gold Foil Experiment”. He proposed the “Nuclear Model”. In 1914 he discovered the lowest charge on an ionized gas particle is from the hydrogen ion.

Question 15

Soddy

Answer 15

discovered that radioactive decay suggests different atoms of the same element.

Question 16

Bohr

Answer 16

using Rutherford’s concept of a nuclear atom, and Planck’s Quantum Theory, proposed the “Planetary Model” for atomic structure.

Question 17

Moseley

Answer 17

determined the charges on the nuclei of most atoms. He realized that the atomic number/number of protons was unique to each element.

Question 18

Aston

Answer 18

his work with mass spectrometers indicates that there are different masses for some atoms of the same element.

Question 19

de Broglie

Answer 19

proposed that matter has both particle and wave-like characteristics (wave-particle duality). de Broglie equation: λ = h/mv

Question 20

Schröedinger

Answer 20

visualized an atom as a positively charged nucleus surrounded by vibrating electron waves. He used mathematical probability to describe the location of electrons in an atom. Electrons are described by four quantum numbers: n, l, ml and ms

Question 21

Chadwick

Answer 21

discovered the neutron through the bombardment of beryllium.