Democritus believed that the universe was composed of atoms, correctly, of course. However, at the time, Plato's and Aristotle's hypothesi were just as valid because everyone was a philosopher. There were no scientists back then.
        
                    
             
        
        
        
Answer:
- have high melting and boiling points
- are hard
- are good conductors of electricity when  dissolved in water
Explanation:
Ionic compounds are compounds that are formed between a metal and non-metal with a significant electronegativity difference. The metals transfers their electrons to the non-metals and the electrostatic attraction of the ions brings about the bonding that forms the compound. 
Ionic compounds are diverse in nature and form. 
Here are some of their properties: 
- They are usually hard solids with a high melting point or liquids with high boiling points
- They are soluble in water and non-soluble in non-polar solvents
- They are able to conduct electricity in molten form. 
- They undergo very fast reaction in aqueous solutions. 
 
        
             
        
        
        
Ions have an extra or lost an electron. Isotopes have different numbers of neutrons.
        
             
        
        
        
Answer: the electric charge
Explanation: