Band gap energy comparison

  • Thread starter amm508
  • Start date
Hi,

Which of ZnS and CdSe will have the larger band gap energy, explain.

The answer is given as Zinc sulfide will have a larger band gap energy than cadmium selenide. Both
are II-VI compounds, and Zn and S are both higher vertically in the periodic table than Cd and Se. In moving from bottom to top up the periodic table, band gap energy increases.

I don't understand why moving from bottom up in the periodic table increases bang gap energy. Is it because electronegativity increases?

Would really appreciate if anyone could explain this!

Thank you v much in advance.
 

TeethWhitener

Science Advisor
Gold Member
1,335
724
I don't understand why moving from bottom up in the periodic table increases bang gap energy. Is it because electronegativity increases?
This is one way of thinking about it. More precisely, the difference in electronegativities increases going from CdSe to ZnS. What this means is that ZnS is more ionic in character, so the electrons in the crystal tend to stay more localized to one center than spreading out over multiple centers.
 

Want to reply to this thread?

"Band gap energy comparison" You must log in or register to reply here.

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top