Mg is a conductor, a metal even though the 3s band is filled. The reason is that
ID: 1043588 • Letter: M
Question
Mg is a conductor, a metal even though the 3s band is filled. The reason is that the 3p orbital overlaps. Si is on the same row of the periodic table, and is a semiconductor. What trend across the periodic table would account for the difference in electrical conductivity between two elements? Explain why this trend affects conductivity. Mg is a conductor, a metal even though the 3s band is filled. The reason is that the 3p orbital overlaps. Si is on the same row of the periodic table, and is a semiconductor. What trend across the periodic table would account for the difference in electrical conductivity between two elements? Explain why this trend affects conductivity.Explanation / Answer
As we go across the periodic table no. of electrons in an atom increases due to which bonding characteristic of elements changes. Mg is a conductor whereas Si is in the same row but it's a semiconductor, there are few reasons behind it. As mentioned above that 3p orbitals overlap and Mg or other similar metals have partially filled energy bands through which electrons can move whereas in elements like Si energy bands are filled with electrons. That is why there is no space for electrons to move until the temperature is increased, in which case electrons can be thermally excited to empty bands. That is why we see that electronic conductivity is decreased as we move from left to right in the periodic table, as the free space for electron motion is decreased because energy band is getting filled as we move across the table. An example of this phenomenon is that when the temperature is increased the conductivity of metals start decreasing as valence electron gets scattered more because of lattice vibrations whereas insulators and semiconductors become better conductor at high temperature because electrons get thermally excited to empty energy bands. Another reason is the bonding nature of these two elements, Si atoms bond perfectly to four neighbouring atoms making strong covalent bonds and leaving no free electrons for electronic conductions whereas metals like Mg have metallic crystals with free electrons that can move easily between atoms making them good conductor.