Ncert Exercises & Solutions

Which of the following statements related to the modern periodic table is incorrect?

1.	The p-block has 6 columns, because a maximum of 6 electrons can occupy all the orbitals in a p-shell.
2.	The d-block has 8 columns, because a maximum of 8 electrons can occupy all the orbitals in a d-subshell.
3.	Each block contains a number of columns equal to the number of electrons that can occupy that subshell.
4.	The block indicates the value of the azimuthal quantum number (l) for the last subshell that received electrons in building up the electronic configuration.

Hint: The d-block has 10 columns because a maximum of 10 electrons can occupy all the orbitals in a d-subshell.

p-block: Has 6 columns (groups 13 to 18) because a p-subshell has 3 orbitals × 2 electrons, each = maximum 6 electrons. This is correct (statement 1 is true).
d-block: Has 10 columns (groups 3 to 12) because a d-subshell has 5 orbitals × 2 electrons, each = maximum 10 electrons. Statement 2 wrongly says "8 columns" and "8 electrons" — this is incorrect.
Statement 3: Generally true — the number of columns in each block corresponds to the maximum electrons that can occupy that subshell (s = 2, p = 6, d = 10, f = 14).
Statement 4: Correct. The block (s, p, d, f) is defined by the azimuthal quantum number (l) of the last subshell being filled in the electronic configuration (l = 0 for s, 1 for p, 2 for d, 3 for f).

Conclusion: Only statement 2 is factually wrong. The d-block has 10 groups, not 8.