Atomic theory

Which parts of Daltons hypothesis are still supported by modern atomic theory? 

1-Matter is made up of atoms, and they are the smallest unit of an element 

2-Atoms of different elements have different properties 

3-Compounds are made up of two or more elements 

4-Matter cannot be created or destroyed 

Which parts of Daltons hypothesis do we know are untrue today? 

-Atoms are all identical, this is later proved to be untrue since the discovery of Isotopes 

-Isotopes have the same number of protons but different number of neutrons 

How did Thompsons discovery change atomic theory? 

-It was believed that atoms could not be divided into smaller particles,  

-By using a cathode lamp, Thompson discovered the first subatomic particle the electron 

How were neutrons discovered

-When James Chadwick bombarded beryllium atoms with alpha particles it produced a unknown radiation which was later called the neutron.

 

Describe Thompsons model of the atom 

-Thompson proposed that an atom consisted of a sphere of positive charge with negatively charged electrons spread throughout 

-This was called the Plum Pudding Model 

Why did some particles go through the gold foil experiment while some were deflected? 

-Due to the fact that particles went straight through without being deflected showed that the solid parts of the atom were not spread throughout but instead were concentrated around the centre. 

-The deflection occurred due to the electrostatic repulson between positively charged alpha particles and positively charged particles in the atom which was later called the proton. 

What important discoveries resulted from this experiment? 

-This experiment proved that atoms are mostly made up of empty space 

-They have a very concentrated area of positive charge which Rutherford called the nucleus