Year 11 Chemistry ~ Chapter 2: A particle view of matter
A typical Aluminium can contains approx. 4 000 000 000 000 000 000 000 000 aluminium atoms
packed closely together. Write in Standard notation = __________ If you used jelly beans to
represent the atoms, it would cover the Earth to a depth of 70kms….WOW!
2.1 Inside Atoms
In 1900 experimental evidence suggested that there were particles smaller than an atom…..
that were positively charged and even smaller ones that were negatively charged.
READ: Cathode Rays (Experimental evidence)
*Activity: Produce a flow chart and place in your Study/Revision area.
An Early atomic model
Atoms are too small to see even with a microscope, so scientist use models to help explain.
These models change with time as chemists learn more.
In 1897 J.J Thomson proposed the ‘plum pudding’ model, this model replaced Daltons (solid ball
of matter). By 1900 it was accepted that atoms contained positively charged particles
(_______) and negatively charged particles (_________)
– sub-atomic particles.
*Draw: Thomson’s model and annotate:
QUESTION: 1.
2.2 The Nuclear atom
Ernest Rutherford: His model was very similar to the model that is accepted today. He won a
Nobel Prize in 1908 (disintegration of elements).
Marie Curie: discovered the elements radium and polonium (radioactive). They emit _______
particles (_________ charged). She received a Nobel Prize for Chemistry in 1911 because of
her discoveries and shared one with her husband, Pierre Curie in 1903.
Rutherford used this newly discovered information to fire alpha particles at a piece of gold foil.
*Draw: a diagram of explaining Rutherford’s theory.
How would you find an invisible man in a crowd? ____________________________
Rutherford proposed:




A few after he proposed this he suggested that there must also be other particles in the
nucleus that had significant mass but no charge. What do you think these particles may have
been? ____________________________.
Discovery of the
In 1932 James Chadwick identified this mysterious particle and called it the ________ . He
stated that the nucleus contains both __________ and __________.
Scientists had now discovered three sub-atomic particles:
Frederick Soddy came up with idea of isotopes, in the past scientist had discovered elements
that were very similar: for example Thorium and Thorium-X. They were exactly the same in
properties and basically weight.
*Define: isotopes: _________________________________________________
_______________________________________________________________ .
*Copy table 2.1
Subatomic Particle
Mass relative to a proton Charge
Characteristics of atoms
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* Copy down symbol of carbon:
Using the same convention write out Uranium. The isotope of uranium has 92 protons and 143
neutrons:
Ions
When an atom loses or gains an electron, it produces a charged particle called ______ .
 an ion with more electrons than protons is called: _____________
 an ion with less electrons than protons is called: _____________ .
Sodium atomic number is 11.
Protons
Electrons
Neutrons
Electrons
Neutrons
Write conventrion:
If Sodium loses an electron atomic number is 11.
Protons
Sodium ion =
Example: Oxygen
QUESTIONS: 5, 6, 7, 9
2.3 Arranging Electrons around the Nucleus
Rutherford’s model (1911) proposed that the electrons move in circular orbits around the
nucleus with an electrostatic force of attraction operating between the positive nucleus and
the negative electrons.
Rutherfords model had limitations:
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*Draw: fig 2.13
Refining Rutherford’s model ~ Neils Bohr
Neils Bohr (1913) suggested that the laws of physics applies to large objects and did not apply
to the motion of very small objects. He proposed the following about electrons:
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
*Draw: fig 2.15
When elements are heated electrons absorb energy and jump to a _________ energy state
( __________ ). Electrons then return to the __________ energy state
( ________ ______ ), releasing (emitting) a fixed amount of energy in the form of coloured
light. Electrons can return in a number of different ways.
*Draw: fig 2.16
Bohr’s model is extended ~ Ionisation energies
Define Ionisation energy: ___________________________________________________
_______________________________________________________________________
_______________________________________________________________________
Draw: fig 2.17a and annotate
The determination of ionisation energies for a large number of elements led scientists to
conclude that electrons are grouped in different _______ _________ ( _________ ).
Electrons in the same shell:
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
The different energy levels (shells) can hold different numbers of electrons.
Shell Number
Max number of Electrons
1
2
3
4
n
The way that electrons are arranged around the nucleus is known as the _________________
_____________ of an atom.
*Look at Table 2.3
The outermost shell can never hold more that ___ electrons, regardless of the maximum
possible number for that shell. The next shell must have at least ___ electrons before the
previous shell can continue to fill. The electrons in the outershell are called ______________
_____________.
Would these electrons require the least or most energy to be removed? _________________
It is the valence electrons that are involved in __________ ___________ , and denote the
chemical nature of the element.
*Draw: electron shell diagrams & electronic configurations for: Lithium, Sodium and Potassium
QUESTIONS: 12, 13 & 26.
2.4 Limitation of this model (Bohr)
While the shell diagram represents a great advance in our understanding of the atom, there are
limitations.
Electrons can behave like waves
In 1926 Erwin Schrodinger proposed that electrons behaved as _________ around the
_________. He correctly calculated the electronic energy levels of ___________ and of
larger atoms.
Schrodinger’s description of the atom is known as ______ __________ or ____________
___________. Particles such as ___________, ____________ and ___________ behave
according to the laws of __________ mechanics. The electron is now seen to behave like a
________ of __________ charge, having no definite orbits for electrons. They are thought to
move in regions of space surrounding the nucleus called __________ .
Shells and Subshells

 Within the shells are energy levels of similar energy called __________, these are
labelled ____________ .
 In atoms containing more than one electron, the energies of the subshells, within a shell
will __________ in the order < < < .
 Subshells are made up of_________. Orbitals within a particular subshell are of equal
energy.
Table 2.4 Energy Levels within an atom
Shell Number
Number of Subshells
in Shell
1
1
2
2
3
3
4
4
5
5
Subshell in shell
Number of orbitals
in subshell
*Draw: fig 2.21
 1s < 2s < 2p < 3s < 3d < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d.
Electronic Structures of Elements
Pauli Exclusion Principle ~ Wolfgang Pauli (Australian Scientist) stated: An atomic orbital may
hold a maximum of ____ electrons.
Table 2.5 Maximum number of electrons in subshells
Type of Subshell
Number of Orbitals
s
p
d
f
1
3
5
7
Max. number of
Electrons
Example: Sodium (atomic number ____ )
Example: Iron (atomic number _____ )
Usually written like:
*Draw: atomic theory timeline
QUESTIONS: 14, 23ac, 24, 25, 29, 30, 31 & 32.
Chapter outcomes and key terms (don’t worry about photon & quanta).