1. Periodic Table Basics

2. What is an element?
An element is a substance made of only one kind of atom.

4. Atomic Number
Number of protons

5. Atomic Mass/Mass Number
Number of protons plus the number of neutrons

6. Equal to the number of protons
Number of electrons
Equal to the number of protons

7. Periodic Table
The periodic table is arranged according to atomic number (number of protons).

8. Rows and Columns
Elements are arranged from left to right in rows called periods in order of increasing atomic number.
They are also arranged from top to bottom in columns called groups or families. Elements in the same group/family have similar properties.

9. Electron shell = Energy level
Electron shells
Electron shell = Energy level
Electrons must fill up a shell before they can occupy the next.
Only 2 electrons are allowed in the first shell. 8 are allowed in all others.
The outermost shell is called the valence shell.