Everything around us is made
up of tiny particles called
atoms.
What is an atom?
•the word "atom" is derived from the
Greek word, “atomos” or indivisible
•is the smallest unit of matter that
retains the identity of the substance
•smallest particle of a given element
Atoms are composed of three types of subatomic particles and these are the protons,
electrons, and neutrons.
The nucleus, which is found at the center of the atom contains
protons (positively charged) and neutrons (no charge). The
outermost regions of the atom contain the electrons (negatively
charged).
charged balloons
REPULSION
charged ballpen
uncharged paper
ATTRACTION
Directions: Label the diagram by writing the correct term from
the box.
1.
2.
3.
4.
5.
Nucleus
Proton
Electron
Neutron
Electron shell
6. Which particle of an atom has a negative charge?
7. Which particle of the atom contains no electric
charge?
8. Which particle of the atom features a positive
electric charge?
9-10. Which two sub-atomic particles are located
within the nucleus of an atom?
st
1
Atomic
Model
Joseph John
Thomson
He
discovered
that
atoms have negatively
charged particles, which
he called electrons.
J.J. Thomson discovered ELECTRONS
J.J. Thomson proposed the Plum Pudding Model
Plum-Pudding Model
After the experiment Rutherford observed
the following:
•Most alpha particles were undeflected.
•Some are deflected at smaller angles.
•Few alpha particles deflected almost
back towards the source.
Nuclear Model
Rutherford proposed this Nuclear
Model, wherein protons and
neutrons were concentrated in the
center of an atom and this region is
called nucleus. Electrons are found
outside of the nucleus and are
moving along the orbits or electron
shells.