History Of The Atom Flashcards
What happened to Democritus in 400BC
He ripped a piece of paper in half multiple times , until he couldn’t anymore . He compared this to an atom . Later more discoveries were made
What happened to John Dalton in the early 1800s
He said that substances were made up of atoms that were tiny , hard spheres . He also discovered that each element had its own atoms which would change in mass . He believed that they were building blocks of nature ; they COULDNT be split
What happened to J.J. Thompson in 1897
He concluded that atoms weren’t solid spheres and that they contained smaller negatively chartered particles, he called these ELECTRONS.
Who created the plum pudding model
J.J. Thompson
Why was it called the plum pudding model
Because it showed an atom of positive charge with electrons stuck in it .
What happened to Ernest Rutherford in 1909
He decided to fire positively charged alpha particles into a thin sheet of gold . He was expecting them to pass through (bc of the plum pudding model) . However he discovered tht most passed through but some were deflected. He created the nuclear model . And figured out that there was a tiny positively charge nucleus in the centre . Therefore he can to the conclusion that there was a ‘cloud’ of negative particles and most of the atom was empty space
Who created the first nuclear model of the atom ? And what year was it
1909
Ernest Rutherford
What happened to neils Bohr in 1914
He notice. Tht at when atoms were heated , light gave out a certain amount of energy . He then made his own nuclear model. It suggested that all electrons were contained in the shells. He said that each shell was a fixed distance away from the nucleus and the electrons would orbit the nucleus on them. With no electrons between .
1920s-Rutherford and others . What happened ?
Further experiments led to the discovery that the nucleus could be divided into smaller particles, each of which would have the same charge as a hydrogen nuclei . They later called them protons (with a mass and a charge of +1)
When were protons discovered
Late 1920s
Jakes Chadwick -1932 what happened ?
About 20 years after it was accepted that there was a nucleus in an atom, James carried out an experiment to prove the existence of neutral particles in the nucleus .
These became known as neutrons, particles with no charge and a mass of +1.
This led to a model of an atom very similar to the one we have today
When were neutrons discovered and by who
1932
James Chadwick
