1.3 Arrangement of electrons

Question 1

What did John Dalton put forward in 1803?

Answer 1

Elements are composed of atoms
Atoms are invisible
Atoms in a specific elements are the same- have same mass
Atoms in different elements are not the same (have different mass)
Atoms cannot be broken down

Question 2

Who discovered radioactivity and why was this significant?

Answer 2

Becquerel
Showed that an atom was not indivisible (there are particles inside an atom)
Showed that atoms are not invisible

Question 3

Who discovered the electron? What model was proposed? Describe the model.

Answer 3

J. J Thompson.
The plum pudding model.
As atoms are uncharged, there needs to be a positive charge. The electrons are scattered in a sphere of positive charge like plums in a plum pudding

Question 4

What did Rutherford suggest?

Answer 4

That the most mass and positive charge was in the nucleus

Question 5

What did Bohr propose?

Answer 5

There is a small positive nucleus
Negative electrons orbit nucleus
Electrons can move between shells
This explains how elements can absorb energy and give off light

Question 6

What did Schrodinger propose?

Answer 6

Electrons have properties of waves as well as particles .

There is an electron density where there is a probable cloud of electrons where they may be.