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1.5 Atomic Structure
1.5.1. The Dalton Model
This activity illustrates the uses of Dalton’s model for an atom even
though it is too simple to explain periodic pattern.
Dalton imagined an atom as a single particle which was
tiny, round and solid.
Dalton’s model can be used to:
 show the arrangement of
atoms in solids, liquids and
gases.
 draw diagrams of molecules.
 show
the
arrangement
particles in crystals.
Dalton’s model can’t explain
 why some elements are more
 why some elements can
of
than others.
and others can’t.
1.5.2. Rutherford’s Model.
This activity is concerned with the new atomic model Rutherford’s team
suggested based on experimental evidence about electric charges.
In the Rutherford model there are two particles in an atom.
 The nucleus has a
charge.
 Electrons have a
charge.
Differences between the Dalton and Rutherford Pictures:
 Dalton’s picture shows the atom as a
particle.
 Rutherford’s picture shows the atom as being made up of
smaller particles.
 Dalton said the atom was
.
 Rutherford said the atom was mainly
.
 Dalton’s picture can’t explain
.
 Rutherford’s picture helps explain electrical conduction because the
electrons around the outside of the atom can move from atom to atom.
1.5.3. Atomic Numbers
This activity shows how the atomic number relates to the structure of
Rutherford’s model of the atom.
The atomic number is the same as the value of the nuclear charge:
Element
Atomic
number
Nuclear
charge
Number of
electrons
Hydrogen
Helium
Lithium
Beryllium
Lithium:
Nuclear charge =
3+
Charge on electrons
Overall charge
=
=
The lithium atom is
because the nuclear
charge is equal and opposite to the negative charge on the electrons.
The charges
each other out.