history of atom Flashcards
what other experiments showed existence of protons
further experiments by rutherford and others showed that the nucleus can be divided into smaller particles , which each have the same charge as a hydrogen nucleus. these particles were named protons
James chadwick carried out an experiment which provided evidence for neutral particles in the nucleus which are now called neutrons and this was displayed in a model of atom which was pretty close to modern day accepted version
in early 1800s how was periodic table arranged
in order of atomic mass, many were placed in wrong troop because elements were placed in order of atomic mass and their properties were not taken into account
what happened in 1869 when Dmitri Mendeleev overcame some of the problems in early periodic table
he took out 50 known elements and arranging them into his table of elements
he put the elements mainly in order of atomic mass but did switch that order if the properties meant it should be changed.
gaps were left in the table to make sure that elements with similiar properties stayed in the same groups. some of these gals indicated the existence of undiscovered elements and allowed Mendeleev to predict what their properties might be. when they were found and they fitted the pattern it helped confirm his ideas
what happened in early 20th centuries to confine mendeleev was correct to not put elements in a strict order
the discovery of isotopes
