History Of The Atom

Question 1

Democritus 460B.C

Answer 1

Came up with an atomic theory stating that all matter is made up of small indestructible units called atoms

Question 2

John Dalton 1803

Answer 2

Proposed that elements consisted of atoms that were identical and have the same mass

Question 3

Dmitri Mendeleev 1869

Answer 3

Arranged the elements and created the first periodic table

Question 4

JJ Thompson 1897

Answer 4

Discovered the electrons and in 1904 put forward his plum pudding model which consisted of a ball of positive. charge with negatively charged electrons embedded in it

Question 5

Robert Millikan 1908

Answer 5

He founded the charge of electrons to be 1.60 × 10^-19

Question 6

Ernest Rutherford 1912

Answer 6

Carried out the alpha scattering experiment which led to the conclusion that atoms contained a positively charged nucleas where most of its mass was concentrated.

Question 7

Niels Bohr 1913

Answer 7

Adapted the model to suggest electrons orbit the nucleas at specific distances in energy levels. They can absorb EM radiation and move to a higher energy level, or give out EM radiation and move to a lower energy level

Question 8

James Chadwick 1932

Answer 8

Discovered neutrons