What is matter made out of?
What is energy?
Why does the Sun shine?
It is made of atoms.
- There are 92 naturally occuring kinds of atoms. Eg
- H hydrogen
- He helium
- Li lithium
- Be beryllium
- B boron
- C carbon
- N nitrogen
- O oxygen
- Fe iron (26)
- the last is U uranium (92)
- Atoms are often stuck together in molecules. Eg.
- H2O water
- CO carbon monoxide
- H2 hydrogen
- Atoms are small, about 10-10 m in diameter for the smaller
Atoms are made of electrons moving around a nucleus.
- Electrons are light particles with negative electric charge.
- As far as one can determine by experiments, they have zero size.
- Nuclei are heavy particles with positive electric charge.
- Experiments show that the size of a nucleus is about 10-15 m
in diameter for the smaller ones.
- Nuclei are made of protons and neutrons.
- Positively charged particles attract negatively charged particles.
That's what holds atoms together.
- In very hot places (eg. stars) the electrons can get ripped off
of the atoms. An atom that is missing one or more of its electrons
is called an ion.
- Here is a tour of the atomic world.
With this knowledge about matter, we can discuss why it is
a sunny day today.
Davison E. Soper, Institute of Theoretical Science,
University of Oregon, Eugene OR 97403 USA