Important questions based on NCERT syllabus for Chapter 5 - Periodic Classification of Elements:
Question-1: How will the tendency to gain electrons change as we go from left to right across a period? Why?
Solution: 1. On moving from left to right across a period, metallic character decreases and non-metallic character increases.
2. Since metals tend to lose electrons and non-metals tend to gain electrons, the tendency to gain electrons increases as we move from left to right across a period.
Question-2: How and why does the atomic size vary as you go:
- From left to right across a period?
- Down a group?
Solution: 1. Atomic size decreases on moving from left to right across a period. This is due to the increase in nuclear charge which tends to pull the electrons closer to the nucleus and reduces the size of the atom.
- Atomic size increases on moving down a group. This is due to addition of new shells which increases the distance between the outermost electrons and the nucleus even though nuclear charge increases.
Question-3: What were the limitations of Newland’s Law of Octaves?
Solution: The limitations of Newland's Law of Octaves are:-
- It was not valid for elements beyond calcium.
- When new elements like noble gases were discovered, his table had no place for them.
- Placing of iron far away from cobalt and nickel, which have similar properties as iron, could also not be explained.