I want to know what is the structural formula of an atom?What do you mean by double bond and single bond? What is Electronegative and Electropositive elements?How can we say that Oxygen is more electronegative than Chromium?Is their any chart of electronegative elements like metal reactivity series?

What type of questions asked from the lesson of magnetic effect of electric current 

Wavelength of green light is

A) 400-450 nm

B) 500-550 nm

C) 660-720 nm

D) 720-800 nm

What is the difference between anaerobic & aerobic respiration? Name some organism that uses the aerobic mode of respiration?

What are the main components of our environment? Explain each of them briefly.

What are examples of hydrotropism plants?