1. Which group elements are called Chalcogen?

2. For the actual value of 4-quantum numbers, which one is the correct set of the electrons in the outer most energy level of $\mathrm{Mg}$ ?

3. Which one of the following values of $R_{f}$ is acceptable for paper chromatography?

4. Electronegativity value of $A$ and $B$ are 21 and 2.5 respectively. The compound formed by A & B -

i. polar

ii. non-polar

iii. covalent

Which one is correct?

5. What is the real cause of the different of physical state of $\mathrm{A}_{2} \mathrm{~B}$ and $\mathrm{A}_{2} \mathrm{X}$ ?