P1.1 + P.2 Flashcards
What is an atom
The smallest part of an element
Rough width of an atom
1 x 10-10m
What was Democritus the first to do
Suggest matter could not be divided for ever and so it is made of atoms
What did John Dalton think about atoms (4 marks)
Draw a model of his atomic theory
Atoms are tiny invisible particles
Atoms of one element are all the same
Atoms of different elements are all different
Compounds are formed by joining atoms
Solid sphere
What did JJ Thomson discover (3 marks)
Draw a diagram of his model
The existence of electrons
They were discovered using cathode rays
He proved atoms were visible
Plum pudding model
Spherical cloud of positive charge with electrons floating inside
What experiment did Earnest Rutherford do and who did he work with
Gold foil experiment
Hans Geiger and Earnest Marsdon
What was the gold foil experiment? *
(3 marks)
What did it prove?
(2 marks)
Draw his model
Alpha particles were sent towards a sheet of gold foil
They were expected to go straight through (as atoms were just spherical clouds) but some bounced back and some deflected slightly
Atoms must have a dense positive centre made from positive atoms called protons
The rest of the atom was mostly empty space
Spherical cloud with positive nucleus and negative electrons floating inside
What was Neil Bohr’s opinion on the Rutherford model
Draw his model
The electrons should be attracted to the nucleus (p to n)
To solve this he decided electrons must move in shells
Positive nucleus
Electrons moving in shells
What was Neil Bohr’s opinion on the Rutherford model
Draw his model
The electrons should be attracted to the nucleus (p to n)
To solve this he decided electrons must move in shells
Positive nucleus
Electrons moving in shells
James Chadwick’s idea
Draw his model
Nucleus double theoretical mass
This meant neutrons had to exist
P+ and n making up nucleus and e- orbiting in shells
Where is most of the mass of an atom carried
Nucleus
What charge do atoms have
Neutral
What is the ratio of protons and electrons in an atom
1:1
How to work out number of
P+
E-
N
P+ = atomic number
E- = P+
N = mass number - atomic number
What is density
Amount of mass in a certain volume of material
How packed in a material is
