CHEMICAL BONDS , IONIC BOND

CHEMICAL BONDS

         The forces that hold together the atoms of a molecule or a compound

          An atom will form a chemical bond with another atom depending upon the number of electrons in its outer most shell or valence shell

CHEMICALLY STABLE ATOM

              An atom with a valence shell holding 8 electrons

             is unlikely to form chemical bonds with another atoms.

             eg. Neon
                        atomic number - 10 = 2, 8

                        8 electrons in valence shell

                        it does not bond easily with another atom.  


              Helium

                      Helium has 2 valence electrons
                        it is stable.

                    seldom bonds with another atoms

            Hydrogen

                 has only 1 valence electron

                 so it binds readily with other atoms. 


OCTET RULE

OCTET= set of 8

Two or more atoms interact in ways that produce a chemically stable arrangement of 8 valence electrons for each atom.

  

3 TYPES OF CHEMICAL BONDS

1. IONIC
2. COVALENT
3. HYDROGEN

IONIC BOND

        Force of attraction that holds together ions with opposite charges.

        eg. NaCl

           a. sodium=  Na

             atomic number=11

               2, 8, 1

            sodium has one valence electron

           A sodium atom can have a complete octet of electrons in its  outer most shell by losing 1 electron.
                    then total number of protons= 11
                   total number of electrons= 10

Thus sodium atom has become a cation or positively charged ion.

         A sodium ion has an charge 1+ 
                      is written Na +

b. chlorine- Cl

       atomic number= 17

      2,8,7

      chlorine has 7 valence electrons

A chlorine atom can have a complete octet by gaining 1 electron

   After gaining an electron,
               total number of protons= 17
                total number of electrons= 18

Thus chlorine atom become an anion or negatively charged ion.

A chloride ion has a charge 1-
is written Cl-

IONIC BOND BETWEEN SODIUM AND CHLORINE

When an atom of sodium donates its sole valence electrons to an atom of chlorine

the resulting positive and negative charges pull both ions tightly together 

              forming an ionic bond

                  resulting compound is sodium chloride

written as NaCl


IONIC compounds

exists as solids

with an orderly repeating arrangement of the ions

eg.  A crystal of sodium chloride may be large or small. But the ratio of Na+ to Cl_ is always 1:1.

In body 
          ionic bonds are found mainly in teeth and bones, 
                    where they give great strength to these important structural tissues.

ELECTROLYTE

An ionic compound that breaks apart into positive and negative ions in a solution.

So named because their solution can conduct an electric current.

Most ions in the body are dissolved in body fluids as electrolytes.


COMMON IONS AND IONIC COMPOUNDS IN THE BODY


CATIONS


Hydrogen ion      H+

Sodium ion         Na+

Potassium ion      K+

Ammonium ion   NH4+

Magnesium ion   Mg2+

Calcium ion        Ca2+

Iron ii                 Fe2+

Iron iii                Fe3+



ANIONS


Fluoride ion            F-

Chloride ion            Cl-

Iodide ion                I-

Hydroxide               OH-

Bicarbonate            HCO3-

Oxide                     O2-

Sulphate                 SO4  2-

Phosphate              PO4 3-