Question

Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to $(E_{g})_{c} (E_{g})_{si} (E_{g})_{Ge}$. State if the following statement is ture: $(E_{g})_{c} \ \textgreater \ (E_{g})_{Si} \ \textgreater \ (E_{g})_{Ge}$

Answer 1

Answer ⇒ True. The given sequence is Correct.

The Correct sequence will be,

            $(E_g)_G_e < (E_g)_S_i < (E_g)_C$

Explanation ⇒

We know that the Band gap which is a Energy difference between the top of a valence band and the bottom of the Conduction band.

Now, We know that carbon is  much  more electronegative then the Silicon which is little more electronegative then the Germanium.

As a result of this the electrons are strongly bound in the Carbon atom and then in the Silicon atom and least in the Germanium atom among them.

As a result of this, a more energy is required for the Electron of the Carbon to jump from valence bond to the conduction bond.

Similarly, For Silicon this energy is little less than that of Carbon but it is great than that of the Germanium, due to there Electronegativity difference.

Thus, The Correct Sequence for them will be,          

$(E_g)_G_e < (E_g)_S_i < (E_g)_C$

Mathematical values are written in attachments.

Hope it helps.

Answer 2

We know that the Band gap which is a Energy difference between the top of a valence band and the bottom of the Conduction band.

Now, We know that carbon is  much  more electronegative then the Silicon which is little more electronegative then the Germanium.

As a result of this the electrons are strongly bound in the Carbon atom and then in the Silicon atom and least in the Germanium atom among them.