What Are d-Block and f-Block Elements? (Meaning, Position and Examples)
Chemistry · D And F Block Elements · NEET
d-block elements are the metals in the middle of the periodic table (groups 3 to 12) where the last electron enters a d-orbital. f-block elements are the two rows placed below the main table (lanthanoids and actinoids) where the last electron enters an f-orbital. Memory hook: "d = the big middle block, f = the two rows kept at the bottom."
The d-block is the large middle set of groups 3-12 where the last electron fills a d-orbital; the f-block (lanthanoids and actinoids) is drawn as two rows below the main table where the last electron fills an f-orbital.
Your doubts, answered
What exactly makes an element a d-block or f-block element?
Look at where the last (differentiating) electron goes. If it enters a d-orbital (like 3d, 4d, 5d), the element is a d-block element. If it enters an f-orbital (4f or 5f), it is an f-block element. This is the only rule you need to decide the block. Example: Fe fills 3d, so it is d-block. Ce fills 4f, so it is f-block.
Where are the d-block and f-block elements located in the periodic table?
d-block elements sit in the middle, in groups 3 to 12, between the s-block (left) and p-block (right). f-block elements (the lanthanoids and actinoids) are placed in two separate rows at the very bottom of the table, so the main table stays short and neat. For NEET, remember d = center, f = bottom two rows.
How many series are there in the d-block and f-block?
The d-block has 4 series: 3d (Sc to Zn), 4d (Y to Cd), 5d (La/Hf to Hg) and 6d. The f-block has 2 series: the 4f series called lanthanoids (Ce to Lu) and the 5f series called actinoids (Th to Lr). Knowing this count helps you answer 'which series' questions quickly.
Are d-block elements and transition elements the same thing?
Almost, but not exactly. All transition elements are d-block, but not every d-block element is a transition element. A true transition element must have a partly filled d-orbital in its atom or in a common ion. Zn, Cd and Hg have completely filled d10, so they are d-block but NOT transition elements. NEET loves to test this exception.
Why are f-block elements written separately below the main table?
If the 14 lanthanoids and 14 actinoids were placed inside the main table, it would become very wide and hard to read. So they are shown as two rows at the bottom. Their properties are also very similar to each other, so grouping them together makes sense. They are sometimes called 'inner transition elements' because the f-orbitals being filled are deep inside.
What is the general electronic configuration of d-block and f-block elements?
d-block general configuration is (n-1)d^1-10 ns^0-2, meaning the d-orbital of the inner shell fills while the outer s has 0 to 2 electrons. f-block general configuration is (n-2)f^1-14 (n-1)d^0-1 ns^2, meaning the f-orbital that is two shells inside is being filled. This is why f-block elements are called inner transition elements.
⚠️ The NEET trap ✗ Zn, Cd and Hg are transition elements because they are in the d-block. ✓ Zn, Cd and Hg are d-block elements but NOT transition elements, because their d-orbital is completely filled (d10) in both the atom and its common +2 ion. 🧠 Being in the d-block only makes you a d-block element. To be a 'transition element' you also need a partly filled d-orbital. Full d10 = out of the transition club.
Real NEET questions
NEET 2017
The reason for greater range of oxidation states in actinoids is attributed to:
A · The radioactive nature of actinoids
B · Actinoid contraction
C · 5f, 6d and 7s levels having comparable energies ✓
D · 4f and 5d levels being close in energies
Solution: Actinoids are the 5f-block (f-block) series. In these elements the 5f, 6d and 7s energy levels are very close in energy, so electrons from all three can take part in bonding. This lets actinoids show a wide range of oxidation states (unlike lanthanoids, whose 4f electrons are buried deeper and mostly give only +3). Option (d) is wrong because it names 4f and 5d, which belong to lanthanoids, not actinoids.
NEET 2016 Phase 1
The electronic configurations of Eu (Z=63), Gd (Z=64) and Tb (Z=65) are:
A · [Xe] 4f7 6s2, [Xe] 4f8 6s2 and [Xe] 4f8 5d1 6s2
B · [Xe] 4f6 5d1 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2
C · [Xe] 4f6 5d1 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f8 5d1 6s2
D · [Xe] 4f7 6s2, [Xe] 4f7 5d1 6s2 and [Xe] 4f9 6s2 ✓
Solution: These three are f-block (lanthanoid) elements, so the last electrons fill the 4f orbital. Eu (63) = [Xe] 4f7 6s2 (stable half-filled 4f7). Gd (64) = [Xe] 4f7 5d1 6s2 (the extra electron goes to 5d to keep the stable 4f7, not into 4f). Tb (65) = [Xe] 4f9 6s2. This matches option (d). The key idea: f-block means the differentiating electron enters the f-orbital, and half-filled 4f7 gives extra stability.
NEET 2021
Zr (Z=40) and Hf (Z=72) have similar atomic and ionic radii because of:
A · Lanthanoid contraction ✓
B · Having similar chemical properties
C · Belonging to the same group
D · Diagonal relationship
Solution: Zr is a 4d-block element and Hf is a 5d-block element in the same group. Normally the 5d element should be much larger, but the 14 f-block lanthanoids come just before Hf. Filling the poorly-shielding 4f orbitals causes lanthanoid contraction, which pulls Hf's size down so it nearly equals Zr. This is a direct example of how filling the f-block affects d-block sizes.
Solved D And F Block Elements NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The d-block and the transition series overlap a lot but are not identical. The d-block is defined only by position (groups 3-12) and by the last electron entering a d-orbital. A transition element has the extra rule of a partly filled d-orbital, so Zn, Cd and Hg are d-block but not transition elements.
What are inner transition elements?
Inner transition elements are the f-block elements, that is the lanthanoids (4f) and actinoids (5f). They are called 'inner' because the f-orbitals being filled lie deep inside the atom, two shells below the outermost shell.
How many elements are in the d-block and f-block?
The d-block has about 40 elements across its 4 series (each series can hold up to 10 d-electrons). The f-block has 28 elements: 14 lanthanoids plus 14 actinoids, since each f-subshell holds up to 14 electrons.
Why is this topic important for NEET?
Nearly every year NEET asks 1-2 questions from the d- and f-block chapter, often on identifying the block, electronic configuration, oxidation states, or lanthanoid contraction. Getting the basic 'what is d-block vs f-block' idea right lets you solve those questions in seconds and avoid the Zn/Cd/Hg trap.
Which orbital is being filled in f-block elements?
In f-block elements the (n-2)f orbital is being filled: 4f for the lanthanoids and 5f for the actinoids. That is why their general configuration is (n-2)f^1-14 (n-1)d^0-1 ns^2.
