1. Atoms Atoms are the building blocks of elements.
They are made up of three subatomic particles:
1) protons – are found in the nucleus and have a positive charge.
2) neutrons – are also found in the nucleus, but have no charge.
3) electrons – orbit around the nucleus and have a negative charge.

2. Electrons can jump through space and change the charge on an atom.
When the number of electrons equals the number of protons the atom will have no charge.
= electrons
= protons p p
= neutrons p

3. When the number of electrons is greater than the number of protons the atom will have a negative charge.
= electrons
= protons p p
= neutrons p

4. When the number of electrons is less than the number of protons the atom will have a positive charge.
= electrons
= protons p
= neutrons p p

5. Dalton's Atomic Theory
John Dalton ( ) was an English chemist, meteorologist, and physicist. He is best known for his pioneering work in the development of the modern atomic theory.

6. All matter is made up of small particles called atoms.

7. 2) Atoms of one type of element are identical to each other, but are
different from atoms of other elements.
Sodium Atom
Silver Atom

8. 3) Atoms cannot be created nor destroyed by ordinary means.
Not By…

9. 4) Atoms may combine with other atoms to form larger particles called molecules.

10. Why is this important? Nuclear Energy is energy from atoms
Nuclear energy is energy in the nucleus (core) of an atom. There is enormous energy in the bonds that hold atoms together.

11. Nuclear energy can be used to make electricity.
But first the energy must be released. It can be released from atoms in two ways: nuclear fission or nuclear fusion.
In nuclear fission, atoms are split apart to form smaller atoms, releasing energy!

12. How many protons, neutrons, and electrons are there in an atom?
The number of protons in an atom is called the atomic number.

13. The number of protons and electrons in an atom is the same.

14. Finally, we have the mass number (atomic mass).
The mass number represents the sum of protons and neutrons in an atom.
Number of neutrons = mass number – atomic number