Periodic Classification of Elements — Questions & Answers

Sample questions from Periodic Classification of Elements

1. Q1. The vertical columns in the periodic table are called:

   • A.groups✓
   • B.periods
   • C.shells
   • D.series only
   Solution

   The periodic table has eighteen vertical groups.

2. Q2. The valency of group 1 elements is generally: Compare the same trend in a second pair:

   • A.1✓
   • B.2
   • C.7
   • D.0
   Solution

   Group 1 atoms lose one valence electron.

3. Q3. An element in period 3 and group 18 is likely:

   • A.argon✓
   • B.sodium
   • C.chlorine
   • D.magnesium
   Solution

   Argon has three shells and a complete outer shell.

4. Q4. Going down a group, the tendency to lose electrons increases and the tendency to gain them falls. The single reason for BOTH is:

   • A.The atomic mass increases
   • B.The atom becomes larger, so the outermost shell is further from the nucleus and less firmly held by it✓
   • C.The number of protons falls
   • D.The elements become heavier and slower
   Solution

   B is correct: a valence electron further from the nucleus is more easily lost, which makes the metals more reactive down group 1, and an incoming electron is held less strongly at that distance, which makes the halogens less reactive down group 17. A is true but explains nothing by itself. C is false, since the nuclear charge increases down a group. D is not a chemical statement at all.

5. Q5. Why are noble gases chemically unreactive?

   • A.Their outermost shells are complete✓
   • B.They have no electrons
   • C.They are all metals
   • D.They have one valence electron
   Solution

   A complete valence shell gives high stability.

Other Class 10 Chemistry chapters