Ionic Bonding

• Ionic bonding - transfer of electrons
• When a metal and a non-metal react together, the metal atom loses electrons to form a positively charged ion and the non-metal gains these electrons to form a negatively charged ion. These oppositely charged ions are strongly attracted to one another by electrostatic forces. This atraction is called an ionic bond
• Dot and cross diagrams show how ionic compounds are formed
• Dot and cross diagrams show the arrangement of electrons in an atom or an ion. Each electron is represented by a dot or a cross. So these diagrams can show which atom the electrons in an ion originally came from
• Sodium chloride (NaCl)

  The sodium atom gives up its outer electron, becoming an Na+ ion. The chlorine atom picks up the electron, becoming a Cl- (chloride) ion

  
• You can work out how many electrons an atom will gain or lose from its group number
• Here the dots represent the Na electrons and the crosses representthe Cl electrons

  
• Magnesium oxide (MgO)

  The magnesium atom gives up its two outer electrons, becoming an Mg2+ ion. The oxygen atom picks up the electrons, becoming an O2- (oxide) ion

  
• Magnesium chloride (MgCl2)

  The magnesium atom gives up its two outer electrons, becoming an Mg2+ ion. The two chlorine atoms pick up one electron each, becoming two Cl- (chloride) ions

  
• Sodium oxide (Na2O)

  Two sodium atoms each give up their single outer electron, becoming two Na+ ions. The oxygen atom picks up the two electrons, becoming an O2- ion

  
• Dot and cross diagrams are useful for showing how ionic compounds are formed, but they don't show the structure of the compound, the size of the ions or how they're arranged