Question

(a) calculate %ic of the interatomic bonds for the intermetallic compound al6mn. (b) on the basis of this result what type of interatomic bonding would you expect to be found in al6mn?

Answer 1

The answer is:

a)0.25%

b) metallic bond

The explanation:

A) The percentage of ionic character in a compound having some covalent character can be calculated by the following equation. The percent ionic character = Observed dipole moment/Calculated dipole moment assuming 100% ionic bond × 100.

-The percent ionic character is a function of the electron negativities of the ions XA and XB .  The electronegativities for Al and Mn  are 1.5 and 1.6, respectively :

when %IC = [1-exp(-1/4) (XB-XA)^2].100

so, %IC =  [1  -  exp(- 0.25)(1.6- 1.5)^2] .  100 = 0.25%

 

(b) Because the percent ionic character is so small (0.25%) and this intermetallic compound is composed of two metals Al and Mn, the bonding is completely metallic.

Metallic bond:

• Metallic bonding can be either weak (68 kJ/mole or 0.7 eV/atom for Hg) or strong (850 kJ/mole or 8.8 eV/atom for W)

• Metallic bonding gives rise to high electrical and thermal conductivity.

-The electrons are loosely held since each atom has several unoccupied valence orbitals; it is relatively easy for the electrons to move about. In this manner the electrons allow atoms to slide past each other.