C1 Flashcards
Summarise JJ Thompson’s findings and resulting theory
J J Thomson found that atoms contain even smaller, negatively charged particles - electrons.
He proposed a new theory in which the atom was a ball of positive charge, with discrete electrons throughout it. It was known as the ‘plum pudding model
Why do atoms have neutral charge ?
Because they have the same number of positive protons and negative electrons so the charges cancel out
Describe structure of solids
Particles are fixed in a regular arrangement.
Particles are very close together.
Particles vibrate.
Strong forces of attraction between the particles.
Summarise the experiment carried out by Ernest Rutherford, and its results.
Experiment: Ernest Rutherford and his student conducted the alpha particle scattering experiments where they fired positively charged alpha particles at an extremely thin sheet of gold.
Results: Rather than all of the alpha particles passing straight through the sheet of gold as you would expect from the plum pudding model, some were deflected to the side, and a small number were even deflected backwards
Why do solids expand when heated?
Solids expand when heated because the particles gain more (kinetic) energy, and so vibrate more.
What does the “atomic number” of an atom tell you?
The number of protons the atom has
What was the ‘plum pudding model’, and who proposed it?
The ‘plum pudding model’ was a theory proposed by J J Thompson in which the atom is a ball of positive charge, with discrete electrons throughout it. Like a ‘pudding’ with bits of ‘plum’ spread throughout it.
Describe the structure of liquids.
Particles are arranged randomly.
Particles are close together.
Particles are free to move in random motion (in all directions).
Medium forces of attraction between the particles
Summarise John Dalton’s theory
John Dalton described atoms as solid spheres, and said that different-sized spheres made up the different elements.
Describe the structure of gases.
Particles are arranged randomly.
Particles are far apart.
Particles are free to move in random motion (in all directions).
Weak/no forces of attraction between the particles.
What is the formula for relative atomic mass?
RELATIVE ATOMIC
MASS (A,)
=
SUM OF:
(ISOTOPE ABUNDANCE X ISOTOPE MASS NUMBER/
SUM OF ABUNDANCES OF ALL ISOTOPES
What is the nuclear model of the atom, and who proposed it?
Proposed by Ernest Rutherford.
The nuclear model of the atom is the idea that each atom is composed of a small positively charged nucleus at the centre, surrounding by a ‘cloud’ of negative electrons.
What was the main issue with the nuclear model of the atom?
The atoms in theory should just collapse
What is the particle model (or kinetic model)? Include its assumptions.
A simple model in which solids, liquids, and gases, can be represented as lots of particles. It assumes that all substances are made from small, inelastic spheres.
What did James Chadwick discover?
James Chadwick discovered neutral particles called neutrons.
