s blockGroups 1 and 2, with helium. An s subshell holds two electrons, so the block is two columns wide. Helium fills 1s and belongs here, though it is printed at the top of group 18.
p blockGroups 13 to 18, without helium. A p subshell holds six electrons, so the block is six columns wide.
d blockGroups 3 to 12, ten columns wide. A d subshell holds ten electrons. Its number is one less than the period.
f blockThe two rows set below the table. An f subshell holds fourteen electrons. The rows belong in periods 6 and 7, and the number is two less than the period.
The subshell each row fills 19
1sPeriod 1: hydrogen and helium. Helium stands at the far right, but its two electrons are in 1s.
2sPeriod 2, groups 1 and 2. Lithium and beryllium.
2pPeriod 2, groups 13 to 18. From boron to neon.
3sPeriod 3, groups 1 and 2. Sodium and magnesium.
3pPeriod 3, groups 13 to 18. From aluminum to argon.
4sPeriod 4, groups 1 and 2. Potassium and calcium.
3dPeriod 4, groups 3 to 12. From scandium to zinc. The number is one less than the period.
4pPeriod 4, groups 13 to 18. From gallium to krypton.
5sPeriod 5, groups 1 and 2. Rubidium and strontium.
4dPeriod 5, groups 3 to 12. From yttrium to cadmium. The number is one less than the period.
5pPeriod 5, groups 13 to 18. From indium to xenon.
6sPeriod 6, groups 1 and 2. Cesium and barium.
4fThe upper row set below the table. Period 6, from lanthanum to ytterbium. The number is two less than the period.
5dPeriod 6, groups 3 to 12. From lutetium to mercury. The number is one less than the period.
6pPeriod 6, groups 13 to 18. From thallium to radon.
7sPeriod 7, groups 1 and 2. Francium and radium.
5fThe lower row set below the table. Period 7, from actinium to nobelium. The number is two less than the period.
6dPeriod 7, groups 3 to 12. From lawrencium to copernicium. The number is one less than the period.
7pPeriod 7, groups 13 to 18. From nihonium to oganesson.
How this list was compiled: Read on 2026-10-03. (1) Purdue University, general chemistry topic review, Quantum Numbers and Electron Configurations (https://chemed.chem.purdue.edu/genchem/topicreview/bp/ch6/quantum.html): the order in which the subshells fill, 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p; the room in an s, p, d and f subshell (2, 6, 10 and 14 electrons); and the place of each on the table: the two columns on the left for s, the next ten for d, the six on the right for p and the fourteen at the bottom for f. (2) Wikipedia, English edition, Block (periodic table): the s block is groups 1 and 2 with helium, which is an s element though it is nearly always printed in group 18; the p block is groups 13 to 18 without helium; the d block is groups 3 to 12; the f block runs from lanthanum to ytterbium and from actinium to nobelium, and many tables instead shift it one box so that lanthanum and actinium stand in the d block. (3) The PubChem periodic table of the U.S. National Institutes of Health (https://pubchem.ncbi.nlm.nih.gov/rest/pug/periodictable/JSON): the symbol, name and ground-state electron configuration of each of the 118 elements; a strip ends where its subshell is full (zinc 3d10, ytterbium 4f14, mercury 5d10, nobelium 5f14). (4) IUPAC, Periodic Table of Elements (https://iupac.org/what-we-do/periodic-table-of-elements/): the layout, and the note that the make-up of group 3 (lutetium and lawrencium, or lanthanum and actinium) is an open question. Licence: own work
The drawing: Drawn for this site by script on 2026-10-03 from the list of elements in each region. Only the arrangement follows the common 18-column table; the drawing is new. Own work. Licence: own work
How it works
Here are the orbitals labeled on the periodic table: first the s, p, d and f blocks, then a strip for each subshell, from 1s to 7p. Tap a region to read about it, then press Quiz me.
Read the full guide
Periodic table, labeled: orbitals by block
The first table shows four blocks. The two columns on the left fill an s subshell, the ten in the middle a d subshell, the six on the right a p subshell, and the fourteen set below an f subshell.
The subshell each row fills
The second table cuts each row into strips, in the order they fill: 1s, 2s, 2p, 3s, 3p, 4s, 3d and on to 7p. An s or p strip takes the number of its period; a d strip is one less and an f strip two less.
One box that differs between tables
Here lutetium and lawrencium open the d strips of periods 6 and 7; many class tables print lanthanum and actinium there. Either way a d strip has ten boxes, an f strip fourteen.
The strips show the simple filling order. A few elements, such as chromium and copper, depart from it.
Questions and answers
What are the s, p, d and f blocks of the periodic table?
Sets of elements named for the subshell being filled. The s block is groups 1 and 2 with helium, the p block groups 13 to 18 without helium, the d block groups 3 to 12, and the f block the two rows set below.
Why is helium in the s block?
Its two electrons are both in the 1s subshell, so it is an s element. Tables print it at the top of group 18 because its full shell makes it behave like the noble gases below it.
How many electrons do s, p, d and f subshells hold?
Two, six, ten and fourteen. That is why the blocks are two, six, ten and fourteen columns wide.
Why does 4s come before 3d on the periodic table?
In the filling order 4s comes just before 3d. Potassium and calcium fill 4s, and scandium then starts 3d in the same row, period 4.