Ions

• As atoms pick up and lose electrons, they also gain or lose charges. Charged molecules are called ions. Opposite charges are attracted to each other. An atom that has lost electrons and becomes positively charged will be attracted to any atom with extra electrons. Conversely, like charges repel each other.
  
  

Polar Molecules

• Water is made of a single atom of oxygen and two of hydrogen. The hydrogen and oxygen naturally develop opposite charges as water is formed, which leave the water molecules positively charged on one side and negatively on the other. This characteristic is called polarity.
  
  

Dissolving

• Since water molecules are effectively both positively and negatively charged, they can attract ions of either charge. Polar water molecules attract molecules of ionic substances apart from one another, spreading them throughout the water and eventually completely dissolving them.