p1.1 - particle model

Question 1

Daltons model

Answer 1

1870s
John dalton
model of an atom was a very small indestructible sphere
two ideas:
- all atoms in an element are the same
- atoms in one element are different from the atoms in all other elements

Question 2

Thomsons model

Answer 2

1897
J.J thompson
discovered the electron
two ideas:
- an atom contains negative electrons
- overall atoms have no electrical change, they are neutral

Question 3

Plum-pudding model

Answer 3

1904
J.J thompson
Positive mass with negative electrons embedded in it

Question 4

Rutherford model

Answer 4

1899
Ernest Rutherford
Discovered that some materials emit particles
called these particles alpha particles - they have positive charge
he fired alpha particles at a piece of gold foil (alpha scattering experiment)
some alpha particles went straight through but some were deflected and some even bounced back

to explain his results he decided that an atom is made of a tiny,positively charged nucleus with electrons around the outside
almost all of the mass of an atom is in its nucleus
when alpha particles hit a nucleus theu bounce back

later, scientists discovered nucleus made of protons and neutrons

Question 5

Bohr model

Answer 5

1913
Niels Bohr
suggested electrons can only move in fixed orbits called electron shells around the nucleus.

Question 6

how big is an atom

Answer 6

1 x 10 ^ -10