Bonding and Structure

Bonding and Structure

1. Ionic

   • An Ionic compound is formed between METALS and NON-METALS
   • An Ionic compound consists of a giant structure of ions arranged in a LATTICE.
   • In a GIANT IONIC LATTICE, the OPPOSITELY CHARGED METAL and NON-METAL IONS are held together by STRONG ELECTROSTATIC FORCES OF ATTRACTION.
   • Besides the elements in Groups 1 and 7, other elements that can form ionic compounds include those in Groups 2 and 6
   • DOT AND CROSS DIAGRAMS can represent the atoms and ions involved in IONIC BONDING.
     • Charges in Dot and Cross Diagrams have to cancel each other.
       • This is because the charges on the ions in an ionic compound always cancel each other out.
     • We have to draw all the shells in Ionic Bonding.
   • The formula of an ionic compound shows the ratio of ions present in the compound.
   • An ion is an atom with a charge,

2. Covalent

   • When NON-METALS react together, their atoms SHARE PAIRS of ELECTRONS. This forms molecules.
     • The atoms in the molecules are then held together by the shared pairs of electrons. These are Covalent bonds.
     • There are weak forces between the molecules (INTERMOLECULAR FORCES)
       • When a covalent substance melts or boils, the INTERMOLECULAR forces have to be overcome, NOT the Covalent Bonds.
   • Some covalently bonded substances have giant structures where huge numbers of atoms are held together by a network of covalent bonds.
     • These are sometimes called macromolecules
     • Examples include Diamond , Graphite and Silicon Dioxide

3. Metallic

   • Atoms in metals are tightly packed together which results in LOSS OF OUTERMOST ELECTRONS.
     • This results in the metals being changed into metallic IONS which are then surrounded by a sea of DELOCALISED ELECTRONS
       • This results in STRONG ELECTROSTATIC FORCES OF ATTRACTION between the ELECTRONS and IONS which are called METTALIC BONDS
     • Along a period, electrons increase in outer shells so they are lost more easily
     • Down a group on the periodic table, Electrons are lost more easily due to an increase in distance from the nucleus.
   • Metallic Bonding can exist in any Metallic element which can be in Groups 1 &3 as well as the Transition Metals

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