2010-08-10

Formation of Ionic Bond & Covalent Bond

Formation of chemical bond is one of the important concepts in chemistry. In Chemistry SPM, students are introduced ionic bond and covalent bond in when they were in form 4.

The following video shows the formation of ionic bond by using formation of sodium chloride as an example.
Ionic bond is the strong electrostatic force of attraction that holds the oppositely charged ions.



The following show samples of answer when explaining formation of ionic bond in essay Chemistry SPM.
  • Electron arrangement of sodium atom is 2.8.1
  • A sodium atom donates one electron to achieve stable octet electron arrangement
  • A sodium ion, Na+ is formed
  • This electron is transferred to a chlorine atom with an electron arrangement of 2.8.7
  • A chlorine atom accepts electron from sodium atom to achieve the stable octet electron arrangement
  • Chloride ion, Cl-, is formed
  • The sodium ion, and chloride ion, are attracted to one another by a strong electrostatic force/ionic bond to form an ionic compound, sodium chloride, NaCl.

The following video show formation of covalent bond. 
A bond that is formed when a pair of valence electrons are shared between two non-metal atoms.
There are three type of of covalent bond :
  • single bond
  • double bond
  • triple bond


SPM Corner:
Electron arrangement for atom W : 2. 4
Electron arrangement for atom X : 2.8.7
Electron arrangemnt for atom Y : 2.8.8.2

Based on the given information, explain how two compounds can be formed from these elements based on their electron arrangements.

The two compounds should have different bond types. [10 marks]
[2005]

Guide:
Formation of Ionic Bond:
  • State the electron arrangement of both atoms.
  • Explain how each atom achieve stable electron arrangement. E.g. To achieve stable electrons arrangement, atom Y donates 2 electrons to form Y2+ ion while atom X donate 1 electron to form X+ ion 
  • Explain the ions formed are attracted by strong electrostatic force.
  • Give the formula of the compound formed.
  • Draw the electron arrangement of the compound formed.

Formation of Covalent Bond:
  • State the electron arrangemnt of and the number of valence electrons of each atoms.
  • Explain how many more electrons for each atom to achieve stable electron arrangement. E.g. Atom W need 4 electrons to achieve stable electron arrangement while atom Y needs 1 electron to achieve stable electron arrangement 
  • Explain how do the atoms share electrons. E.g. Atom W contributes 4 electrons for sharing while atom X contribute 1 electrons for sharing.  Each four Y atoms share 1 pair of electrons with one W atoms
  • State the formula of the compound formed.
  • Draw the electron arrangment of the compoud formed.

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