Chemical bonding OCR Salters

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  • Created by: Rockjece
  • Created on: 17-12-13 19:49

Chemical Bonding

Ionic Bonding

  • Most metal atoms have three or fewer outer electrons. A noble gas configuration is reached if these are lost to form positively charged ions (cations). 
  • Most non-metal atoms have more than three outer shell electrons. To become stable, they must become negatively charged ions (anions). 
  • There are limits to how many electrons an atom can pick up. If one electron is gained, the atom becomes an anion with a negative charge. This will repel any more electrons wanting to join the energy level, and so atoms gaining two or three electrons are rare. 
  • It is also hard to remove three or more electrons from an atom, as the ionisation energy increases after each electron is removed. 

  • When metals bond with non-metals, electrons are transferred from the metal atoms to the non-metal atoms. The metal atoms become cations with a positive charge, and the non metals become anions with a negative charge. Opposites attract, and the atoms are held together by an electrostatic attraction. 
  • Electron dot cross diagrams are used to represent the way the atoms bond together. 
  • Each sodium atom loses one electron and each chlorine atom gains an electron. The formula for sodium chloride is NaCl, however this doesn't mean that sodium and chlorine are only found in pairs; they are found in lattices. 
  • The electrostatic force is spread evenly around each sodium cation and chlorine anion. A sodium cation will therefore be able to attract chlorine anions in all directions, and vice-versa. 
  • The chloride cation can attract six sodium anions, therefore the structure formed is a lattice.
  • Any sodium ion within the structure will be surrounded by 6 chloride ions. It will be repelled by the other sodium ions, and so the layers will form with alternating sodium and chloride ions. 

Covalent bonding

  • Non-metallic elements bond with each other by “sharing” electrons. This is called covalent bonding. Shared electrons count as the outer electron for both elements.
  • In this case the Hydrogen is found in pairs, as there are no charges involved in holding the atoms together, so there is no interaction with the other hydrogen atoms.
  • Electron pairs which form covalent bonds are called bonding pairs. 
  • Electrons not involved are called lone


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