Carbon, silicon and germanium atoms have four valence electrons...

Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by

\left(E_g\right)_{\mathrm{C}},\left(E_g\right)_{\mathrm{Si}}

and \left(E_g\right)_{\mathrm{Ge}} respectively. Which one of the following relationships is true in their case?

Options

A\left(E_g\right)_{\mathrm{C}}\gt $\left(E_g\right)_{\mathrm{Si}}$
B\left(E_g^{}\right)_{\mathrm{C}}= $\left(E_g^{}\right)_{\mathrm{Si}}$
C\left(E_g^{}\right)_{\mathrm{C}} \lt $\left(E_g^{\circ}\right)_{\mathrm{Ge}}$
D\left(E_g\right)_{\mathrm{C}}\gt $\left(E_g\right)_{\mathrm{Si}}$

Correct answer

A. \left(E_g\right)_{\mathrm{C}}\gt $\left(E_g\right)_{\mathrm{Si}}$

Step-by-step solution

Carbon, silicon and germanium are semiconductors.

\begin{aligned}& \left(E_g\right)_{\mathrm{C}}=5.2 \mathrm{eV} \& \left(E_g\right)_{\mathrm{Si}}=1.21 \mathrm{eV} \& \left(E_g\right)_{\mathrm{Ge}}=0.75 \mathrm{eV}\end{aligned}

Thus,

\left(E_g\right)_{\mathrm{C}}\gt\left(E_g\right)_{\mathrm{Si}}

and \left(E_g\right)_{\mathrm{C}}\gt

\left(E_g\right)_{\mathrm{Ge}}

NOTE : Elements carbon, silicon and germanium are found in IVA group of periodic table.

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