Topic 1 - Key concepts

Question 1

Plum Pudding Model

Answer 1

JJ Thompson proposed a ball of positive charge with negatively charged electrons embedded in it.

Question 2

Gold Foil Experiment - what they expected

Answer 2

Rutherford fired positively charged alpha particles at a thin sheet of gold.
They were expecting the particles to pass straight through or only be slightly deflected because the positive charge was thought to be spread through the atom

Question 3

What happened in the experiment?

Answer 3

Most particles passed straight through but some were deflected more than expected and so even reflected straight back. This proved the plum pudding model wrong.

Question 4

Rutherford and Bohr’s Nuclear Model

Answer 4

• The atom must have a small positively charged nucleus at the centre
• A cloud of negative electrons surrounds the nucleus. Most of atom is empty space
• However, in the case the electrons would be attracted to the nucleus and the atom would collapse
• Bohr suggested that electrons can only orbit the nucleus in fixed shells

Question 5

atomic number

Answer 5

no. of protons

Question 6

mass number

Answer 6

protons + neutrons

Question 7

Isotopes

Answer 7

Different forms of the same element
same no. of protons diff no. of neutrons

Question 8

Relative Atomic Mass

Answer 8

sum of ( abundance x isotope no.) /
sum of abundance

Question 9

Electronic Configuration

Answer 9

Electrons occupy shells, lowest energy filled first in a 2.8.8 configuration.