Open lesson 1: The structure of the atom

Lesson 1: The structure of the atom
What you need to know:
1. The name of the smaller particles from which atoms are made.
2. Where these particles can be found in the atom.
3. The mass and charge of these smaller particles.
For a long time scientists believed that the atom was the smallest possible piece
of matter in existence and was a very small solid ball. The word ‘atom’ comes
from the Greek word ‘atomos’, which means uncuttable.
At the start of the 20 th century, scientists decided to investigate the structure of
the atom and found that it was not at all like a small solid ball as previously
thought, but was made up of smaller particles called protons, neutrons and
electrons.
In your exam you may be asked to name the three particles that an atom is
made from.
The protons, neutrons and electrons do not simply whizz around randomly but
have a defined structure. The protons and neutrons are found at the centre
of the atom, in the nucleus. The nucleus contains nearly all the mass of an
atom and has a positive charge.
In your exam you may be asked to name the two particles that can be found in
the nucleus of an atom. You may also be asked to state the charge of the
nucleus and where most of the atom’s mass can be found.
The electrons orbit around the nucleus in shells and have a negative
charge. The number of electrons in an atom is equal to the number of protons,
which is why atoms have no overall charge. Electrons have almost no mass,
which is why it can be said that most of the mass of the atom can be found in
the nucleus.
© Studydoctor 2010

Electron
Neutron
Proton
Nucleus
In your exam you may be asked where electrons can be found in an atom.
After studying protons, neutrons and electrons, scientists were able to calculate
the mass and charge of each of these atomic particles. The table below shows
the relative mass and charge of a proton, neutron and electron.
Particle Mass Charge
Proton 1 +1
Neutrons 1 0
Electrons 0 -1
In your exam you may be asked to complete this table, stating the mass and
charge of a proton, neutron and electron.
Scientists are still trying to investigate the structure of the atom, and this is why
the Large Hadron Collider (LHC) was built in Geneva. By smashing protons
together they hope to break the protons apart and be able to find out what the
protons, neutrons and electrons are made from.
In your exam you might be asked to explain how scientists are trying to discover
what protons, neutrons and electrons are made from.
© Studydoctor 2010

Recap:
1. An atom is not the smallest types of matter.
2. Atoms are made from smaller particles called protons, neutrons and electrons.
3. Protons and neutrons are found at the centre of the atom, called the nucleus.
4. Electrons orbit around the nucleus in shells.
5. Protons have a mass of 1 and a charge of 1, neutrons have a mass of 1 but no
charge and electrons have a mass of 0 and a charge of -1.
Further information:
1. Here is a quick explanation of the Large Hadron Collider:
http://www.youtube.com/watch?v=TMPdmDE72AU
© Studydoctor 2010