Topic 3 - Atomic Structure Flashcards
Who proposed the plum pudding model?
J J Thomson
Describe the plum pudding model
A positively charged ‘pudding’ (sphere) with electrons stuck within it
Who conducted the famous gold foil experiment?
Ernest Rutherford
What did the gold foil experiment involve?
Firing alpha particles at an extremely thin sheet of gold.
What was expected to happen during the gold foil experiment, and what really happened?
It was expected (because of the plum pudding model) that the particles would pass straight through the sheet of gold.
Instead, while most went through, lots of particles were deflected.
What did the gold foil experiment discover?
That atoms are mostly empty space
What was Rutherford’s model called?
The nuclear model
Describe the nuclear model
A small, positively charged nucleus at the centre, surrounded by a ‘cloud’ of negative electrons.
Why was the Nuclear Model proved wrong?
Scientists realized that the ‘cloud of electrons’ would be attracted to the positively charged nucleus, which would cause the whole atom to collapse.
Describe the Bohr model
Electrons arranged in shells around the nucleus.
Each shell has a fixed distance from the nucleus, and a fixed energy.
What are isotopes?
Atoms with the same atomic number, but a different mass number
How are isotopes most commonly represented/written ?
Name of element - mass number
eg) Carbon-12
How do you calculate relative atomic mass?
mass number*abundance (repeat for each isotope)
add the numbers together
divide by 100
Relative atomic mass
The average atomic mass of an element
Give a popular example of a pair of isotopes
Carbon-12 and Carbon-13
How is relative atomic mass different to mass number?
Relative atomic mass takes into account all isotopes of an element, whereas the mass number is the mass of a specific isotope of an element
