# Scientists Who Studied Atomic Structure

## 39 terms · Honors Chemistry, Harrison; Chapters 3 & 4: Atomic Structure/Electron Configuration

### Democritus

Scientist/philosopher from about 400 B.C.

### Democritus

Atomos: indivisible particles

Democritus

Early 1800s

### John Dalton

Discovered first modern atomic theory

### John Dalton

Each element is made up of tiny particles called atoms

### John Dalton

All atoms of the same element are identical, but they differ from those of any other element

### John Dalton

Atoms unite in definite ratios to form compounds

### John Dalton

Chemical reactions involve reorganization of the atoms; the atoms themselves are not changed

John Dalton

Early 1900s

### J. J. Thomson

Cathode ray tube/Crooke's tube

### J. J. Thomson

Cathode rays are negatively charged particles

### electrons

Cathode rays were eventually figured out to be ___

### J. J. Thomson

First person to really discover the electron

### J. J. Thomson

Speed of the electron

### e/m=k

Charge/mass ratio for the electron

### amount of charge on the electron

In the ratio e/m=k, e stands for ___

### mass of the electron

In the ratio e/m=k, m stands for ___

### constant

In the ratio e/m=k, k stands for ___

### coulomb

Unit that measures electricity

### k was the same no matter what metal was used for the cathode

How were all electrons discovered to be the same?

### J. J. Thomson

Created "Plum/Rice Pudding Theory" of the atom

J.J. Thomson

### Robert Millikan

Oil drop apparatus

### Robert Millikan

Experimentally found charge of electrons

### Robert Millikan

Using the equation e/m=k, he calculated the mass of the electron

Robert Millikan

### Ernest Rutherford

Fired alpha particles/helium nuclei/positively charged particles at gold foil

### Ernest Rutherford

Deflection of particles led to discarding the "rice pudding" theory

### Ernest Rutherford

Created the nuclear/planetary model of the atom

### Ernest Rutherford

Center of atom is a sphere of positive charge

### Ernest Rutherford

Electrons orbit the nucleus in 3-D space

### Ernest Rutherford

Most of the atom is empty space

### Ernest Rutherford

Predicted the existence of neutrons

### 5

Ernest Rutherford

### Niels Bohr

Modified Rutherford's model of the atom

### Niels Bohr

Stated that electrons must occupy SPECIFIC orbits around the nucleus

Niels Bohr