Write the electron dot structure of ethane molecule, C₂H₆.

What are the various steps in a food chain called?

What is the important function of presence of ozone in earth’s atmosphere?

What makes the earths atmosphere a heterogeneous mixture?

(a) On the basis of electronic configuration, how will you identify the first and the last element of a period?

(b) The stars appear higher from horizon then they actually are. Explain why it is so ?