Ions.
- = negative += positive ions
 An isolated atom is always neutral (no charge)
 Number of protons in isolated atom is + number of electrons
 Protons have positive charge and electrons have negative charge
 Example oxygen
++++++++++=-------( Neutral )
+ + + + + + + + + + = - - - - - - - ( net charge = +1 or +
Now oxygen is represented as O+ =(positive ion)
+ + + + + + + + + + = - - - - - - - -- (net charge = -1 or
Now oxygen is represented as O- = (negative ion)