Which of the following statements related to the modern periodic table is incorrect? (a) The p-block has 6 columns, because a maximum of 6 electrons can occupy all the orbitals in a p-shell. (b) The d-block has 8 columns, because a maximum of 8 electrons can occupy all the orbitals in a d-subshell. (c) Each block contains a number of columns equal to the number of electrons that can occupy that subshell. (d) The block indicates value of azimuthal quantum number (l) for the last subshell that received electrons in building up the electronic configuration.

Which of the following statements related to the modern periodic table is incorrect? (a) The p-block has 6 col

Exercises · 3.34

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

(a) The p-block has 6 columns, because a maximum of 6 electrons can occupy all the orbitals in a p-shell.

(b) The d-block has 8 columns, because a maximum of 8 electrons can occupy all the orbitals in a d-subshell.

(d) The block indicates value of azimuthal quantum number (l) for the last subshell that received electrons in building up the electronic configuration.

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Concept understanding — Periodic Table Blocks

The Intuition: Why "Blocks" at All?

Imagine you're building a house of cards. Each card has a specific shape and a specific place where it fits. The periodic table is like that house — but instead of cards, we have elements, and instead of shapes, we have electron configurations.

The periodic table is arranged in rows (periods) and columns (groups). But if you look closely, you'll notice that the table isn't a perfect rectangle. There's a detached island of elements (the f-block) floating below, and the main body has a strange "staircase" shape. That shape isn't random — it's dictated by which orbital the last electron enters.

That's the core idea: A block is a set of elements whose last electron enters the same type of orbital (s, p, d, or f).

The Precise Statement

Periodic Table Blocks are regions of the periodic table where elements share the same valence subshell — the subshell being filled as you move across that block.

There are four blocks, named after the four types of atomic orbitals:

Block	Orbital being filled	Location in the table	Number of groups
s-block	$ns$	Leftmost 2 columns (Groups 1 & 2)	2
p-block	$np$	Rightmost 6 columns (Groups 13–18)	6
d-block	$(n-1)d$	Middle 10 columns (Groups 3–12)	10
f-block	$(n-2)f$	Two rows below the main table (Lanthanides & Actinides)	14

Note

The "n" in the orbital notation refers to the principal quantum number (the period number). Notice how for d and f blocks, the orbital being filled has a lower n than the period you're in. That's because of the Aufbau principle — orbitals fill in order of increasing energy, and 4s fills before 3d, etc.

How to Read the Blocks

s-block (Groups 1 & 2)

Last electron enters an $s$ orbital.
Examples: Hydrogen ( $1s^1$ ), Lithium ( $2s^1$ ), Beryllium ( $2s^2$ ).
These are highly reactive metals (except H and He). They lose their $s$ electron(s) easily.

p-block (Groups 13–18)

Last electron enters a $p$ orbital.
Examples: Carbon ( $2p^2$ ), Oxygen ( $2p^4$ ), Chlorine ( $3p^5$ ).
This block contains metals, non-metals, and metalloids — the most chemically diverse block.

d-block (Groups 3–12)

Last electron enters a $d$ orbital — specifically, the $(n-1)d$ subshell.
Examples: Iron ( $3d^6$ ), Copper ( $3d^{10}$ ), Zinc ( $3d^{10}$ ).
These are transition metals. They often have variable oxidation states and form coloured compounds.

f-block (Lanthanides & Actinides)

Last electron enters an $f$ orbital — specifically, the $(n-2)f$ subshell.
Examples: Cerium ( $4f^1$ ), Uranium ( $5f^3$ ).
These are inner transition metals. They are placed below to keep the table from being absurdly wide.

Watch out

A common mistake: thinking that the block tells you the group number. It doesn't. The block tells you the orbital type, not the group. For example, both Carbon (Group 14) and Oxygen (Group 16) are in the p-block, but they're in different groups.

Why This Matters

Knowing the block of an element tells you three things instantly:

Which orbital is being filled — the heart of its electron configuration. …

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The d-block has 10 columns (not 8) because a d-subshell can hold a maximum of 10 electrons across its five orbitals. The incorrect statement is (b).

The periodic table's block structure directly reflects electron configuration. Each block (s, p, d, f) corresponds to the type of subshell being filled as we move across periods. The number of columns in each block equals the maximum electron capacity of that subshell, which comes from the number of orbitals multiplied by 2 (Pauli exclusion principle: two electrons per orbital).

Let me examine each statement against this principle.

Statement (a): The p-block has 6 columns

A p-subshell has three orbitals ( $p_x$ , $p_y$ , $p_z$ ), corresponding to the magnetic quantum number $m_l = -1, 0, +1$ when $l = 1$ . Each orbital holds 2 electrons, giving a maximum of $3 \times 2 = 6$ electrons. The p-block indeed spans 6 columns (groups 13–18 in the modern table). This statement is correct.

Statement (b): The d-block has 8 columns

Here's where the error lies. A d-subshell has five orbitals (corresponding to $m_l = -2, -1, 0, +1, +2$ when $l = 2$ ). The maximum electron capacity is therefore $5 \times 2 = 10$ electrons. The d-block spans 10 columns (groups 3–12), not 8. This statement is incorrect.

Watch out

A common confusion arises from the fact that transition metals often show a maximum oxidation state of +8 (like osmium in $\text{OsO}_4$ ), but this has nothing to do with the number of d-block columns. The block width is determined purely by orbital capacity.

Statement (c): Each block contains columns equal to electron capacity

Let's verify this systematically:

Block	Orbitals	Max electrons	Columns in table
s	1	2	2 (groups 1–2)

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

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