Periodic Table.

Periodic Table.

1. Elements and atoms

   • Element
     • An element is a substance made from only one type of atom.
   • Atom
     • An atom is the smallest piece of an element that can exist.

2. Atomic number

   • Every element has a unique atomic number (also known as the proton number). This is the number of protons in the nucleus of each atom.

3. Groups in the periodic table

4. Trends in the periodic table

   • Down the group
     • the number of outer shell electrons is the same
     • the number of complete electron shells increases by one.
   • Across the group
     • the number of outer shell electrons increases by one
     • the number of complete electron shells stays the same.

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