Atoms

Atoms

1. All substances are made of atoms

   • Substances made of only one atom are elements

2. O represents 1 atom of Oxygen. Na2 represents 2 atoms of Sodium

3. Structure

   • Atoms have a small central nucleus made from protons and nuetrons.
     • Around the nucleus are electrons
   • Protons
     • Positive charge
     • Atomic number
       • Number of protons and electrons
   • Neutrons
     • Neutral
     • Sum of protons and neutrons = mass number
   • Electrons
     • Negative charge
   • Number of electrons is equal to the number of protons

4. Electrons travel around the nucleus in shells

   • First shell occupies 2 electrons
   • Other shells occupy a maximum of eight