Covalent bonds - electrons are shared between atoms.

• Atoms with a high electron affinity usually form covalent bonds.
   
• Since both bonding atoms have a high attraction for the electrons, the shared electrons spend most of their time between the two atoms.
   
• The force of attraction between both nuclei and the shared electrons hold the atoms together in a covalent bond.
   
• Multiple pairs of electrons may be shared between atoms, forming multiple bonds.
   
  • The number of electron pairs shared is expressed by bond order.

Chemical bonding is often expressed as percentages of ionic characteristics and covalent characteristics.

• The closer atoms are to each other on the periodic table, the more covalent their bond characteristics.
   
• The farther apart atoms are on the periodic table, the more ionic their bond characteristics.