history of a atom & electronic structure (electron shell rules (3)…
history of a atom & electronic structure
theory of atomic structures has changed over time
2)In1897 jj Thomson concluded from his experiments that atoms weren't solid spheres
3) solid sphere idea of atomic structures had to be changed the new theory was known as the plum pudding model.
1) at the start of the 19 th century john Dalton described atoms as a solid sphere and said that different spheres made up the different elements
4) the plum pudding model showed the atom as a call of positive charge with electrons stuck in it
Rutherford showed the plumb pudding model was wrong
2) from the plumb pudding model they were expecting the particles to pass through the sheet or be slightly deflected at most .
3)the nuclear model of the atom in this there's a tiny positively charged nucleus at the center where most of the mass is concentrated
1) in 1909 Ernest Rutherford conducted a famous experiment they fired positively charged alpha particles at an extremely thin sheet of gold
bohrs nuclear model
2) niels bohrs nuclear model of the atom suggests that all the electrons were contained in shells
3)bohr proposed that electrons orbit the nucleus in fixed shells and arnt' anyway between each shell is a fixed distance from the nucleus.
1) scientist realised that electrons in a cloud around the nuclease of an atom as Rutherford described would be attracted to the nuclease causing the atoms to collapse
4)bohrs theory of atomic structures was supported my many experiments and it helped to explain lots of other scientific observations
further experiments showed the existence of protons
experiment gave the conclusion that the nucleus could be divided into smaller particles each which has the same charge as a hydrogen nucleus
20 years after it was accepted that atoms have nuclei James Chadwick carried a experiment which provided evidence for the neutral particles in the nucleolus.
electron shell rules
3) only a certain number of electrons are allowed in each shell
1st shel :2 2nd shell : 8 3rd shell :8
2) the lower energy levels are always filled first ones closest to the nucleolus
4) atoms are much happier when they have a full electron shells like the noble gases in group 0
1) electrons always occupy shells
5)In most atoms the outer shell is not full ans this makes the atoms want to react to fill it.