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Notes
chemistry
5
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1 The structure of an atom
So what are elements?
● Elements only contain one kind of a substance(pure substance)
● Elements can exist in a collection of:

➡️ scientific name monoatomic
● Pairs with the same element➡️ called diatomic
● More rarely with three atoms➡️ called triatomic
● Single atom

What are Atoms?
An atom is the smallest component of an element that gives an
elements its property
Atoms are indivisible
(cannot be cut up)
Is there any elements in your body? And what
Yes there is elements in your body for example:
● Oxygen
● hydrogen
● nitrogen
● carbon
● calcium
● phosphorus
All atom of a particular element are the same , different element
have different atoms
Scientist had discovered that atoms are made up of smaller particles
called sub-atomic particles
Atoms are made up of three different particles :
● Electrons

● Protons
● Neutrons
These particles are arranged in the same way in every atom
Protons and neutrons:
They are arranged in the centre of the atom in the nucleus
The electron move around (orbit) the nucleus
Every particles have different properties:
● Proton and neutron have the same mass
● Protons have a positive electric charge(+)
● Electrons have a negative electric charge(-)
● Neutrons have no electric charge()
● Protons and neutrons have much more mass that Electrons in
fact electrons does not have any mass
Fact:
There is a lot of space between atom particle-really there's nothing-

There's an electric charge between positive and negative charge
called electrostatic attraction this attraction between proton and
electron is what holds the individual part of an atom
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J thompson discovered electrons
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Most alpha particles went right through
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Some particles had their
paths bent at large angles
...

Jack chadwick also worked with thompson and rutherford and proved
that neutrons do exist
Bohr theory of atomic structure that explains the spectrum of
hydrogen atoms
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REMEMBER THIS:
Mass number= protons + neutrons
Atomic number =Proton number
Proton number = Electrons number
Neutrons = Mass - Protons

Group1 is called alkali metals properties: it get more
reactive when you go down
Group2 is called alkaline earth metals its reactive but not as
much as Group1
Group 3-12 is called transition metal form coloured
compounds
Group 17 is called halogens they are dioatomic molecule 2
atoms per one molecule
Group 18 is called noble gases they are 1-stable

2- inert(not reactive)
This is how sciences develop :
When scientist make a discovery they write about what they
have done and what they think it means sometimes if the
work is very complicated many different scientist may be
involved from other countries but they still work together
this is called collaboration
Each scientist builds on the idea and the discoveries of
others
QUESTIONS:
Explain how thompson’s model of the atom is different from
the one we use today?
Who discovered the electrons?When did they discover it?
Who proved that the neutrons existed?when?
What 2 things did Rutherford discovered about the
structure of an atom
How is Rutherford’s model different from the structure of
the atom?
How is Rutherfoed’s model different from the model
scientist use today

ANSWERS:
Q1 proton
Q2 electrons

Q3 Protons and neutrons
Q4 the individual atom is held by the electrostatic
attraction between the negative and positive
charges(electrons and Protons)
Q5 Thompson model doesn't have any nucleus unlike what we
use today
Q6thompson discovered electrons in 1980
Q7 James chadwick proved that neutron exist in 1932
Q8 Rutherford discovered the proton in 1909 and the
nucleus in 1911
Q9 Rutherford model didn't have any neutrons because they
didn't prove that they exist

Thank you for opening this DOC



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