Labeling a periodic table means adding the numbers, names, and categories that turn a grid of boxes into a useful reference. Whether you’re filling in a blank table for a class assignment or building one from scratch, the process breaks down into a few layers: labeling each element box, numbering the rows and columns, marking the major regions, and optionally adding trend arrows. Here’s how to do each one correctly.
What Goes Inside Each Element Box
Every element cell on a standard periodic table contains four pieces of information, arranged in a consistent layout:
- Atomic number: the whole number at the top of the box. It tells you how many protons are in the atom’s nucleus. Hydrogen is 1, helium is 2, and so on up to oganesson at 118.
- Chemical symbol: the one- or two-letter abbreviation in the center of the box, written large. The first letter is always capitalized; the second (if there is one) is always lowercase. For example, Na for sodium, Fe for iron.
- Element name: the full name, usually printed below the symbol in smaller text.
- Atomic mass: the decimal number at the bottom of the box. This is the weighted average mass of all naturally occurring versions of that element. Carbon, for instance, is listed as 12.011.
Some tables add extra data like electron configuration, electronegativity, or state of matter at room temperature. These are optional. The four items above are the standard minimum.
Numbering Groups and Periods
The columns running top to bottom are called groups, and the rows running left to right are called periods. Getting the numbering right is one of the most common stumbling points.
Since 1988, the official IUPAC convention numbers the groups simply 1 through 18, from left to right. Older textbooks used Roman numerals with A and B designations (like IIA or VIIIB), but that system created confusion because American and European chemists used the A and B labels differently. If your teacher or textbook asks for the older system, follow their version, but for any new table, use 1 through 18. Write these numbers across the top of the table, one above each column.
Periods are numbered 1 through 7, from top to bottom. Write these numbers along the left side of the table, one beside each row. Period 1 has only two elements (hydrogen and helium). Periods 2 and 3 each have eight. Periods 4 and 5 have eighteen. Periods 6 and 7 are the longest, with 32 elements each, though part of their length gets tucked below the main table for space reasons.
Labeling the Lanthanides and Actinides
The two rows that sit below the main body of the table are the lanthanides (elements 57 through 71) and actinides (elements 89 through 103). They’re pulled out and placed underneath simply so the table fits on a page without becoming absurdly wide.
In reality, the lanthanides belong in period 6, slotting in between lanthanum (element 57) and hafnium (element 72). The actinides belong in period 7, between actinium (element 89) and rutherfordium (element 104). To label them properly, write “Lanthanides” to the left of the upper separated row and “Actinides” to the left of the lower one. Many tables also place a small marker or asterisk in the main grid at the spot where each series would normally appear, connecting the separated rows back to their correct location. Together, these two series are sometimes called the inner transition elements.
Marking the S, P, D, and F Blocks
The periodic table is organized around how electrons fill energy levels, and labeling the four orbital blocks makes this structure visible at a glance.
- S block: the two leftmost columns (groups 1 and 2), plus hydrogen and helium. These elements are filling their outermost s orbital.
- D block: the ten columns in the middle (groups 3 through 12). These are the transition metals, filling their d orbitals.
- P block: the six columns on the right side (groups 13 through 18). These elements are filling their p orbitals.
- F block: the lanthanides and actinides sitting below the main table. These elements are filling their f orbitals.
To label these, draw a bracket or shaded region around each block and write the letter (s, p, d, or f) above or beside it. Color coding works well here: many published tables use a different background color for each block.
Drawing the Metal, Nonmetal, and Metalloid Regions
A zigzag line, sometimes called the staircase, cuts diagonally across the right side of the table. It separates metals on the left from nonmetals on the right. The elements sitting directly along this staircase line are metalloids, which share properties of both.
To label this on your table, draw the staircase line starting near boron (element 5) and stepping down through silicon, germanium, arsenic, antimony, tellurium, and astatine. Then label the three regions: write “Metals” on the large left side, “Nonmetals” on the smaller upper-right side, and “Metalloids” along the line itself. You can also shade each region a different color. Metals make up the vast majority of elements, covering most of the table. Only about 22 elements are nonmetals, and roughly 6 to 8 sit on the metalloid boundary, depending on which classification your source uses.
Adding Common Group Names
Several groups have traditional family names that are worth labeling, especially for chemistry classes:
- Group 1: Alkali metals (excluding hydrogen)
- Group 2: Alkaline earth metals
- Groups 3–12: Transition metals
- Group 17: Halogens
- Group 18: Noble gases
Write these names above or below the group number for each column. Some tables also label group 16 as chalcogens and group 15 as pnictogens, though these names come up less often in introductory courses.
Labeling Periodic Trends
If your assignment asks you to show periodic trends, you’ll add arrows along the edges of the table to indicate the direction each property increases.
Electronegativity, which measures how strongly an atom attracts electrons in a bond, increases as you move right across a period and up within a group. Draw one arrow pointing right along the bottom of the table and another pointing up along the right side. Ionization energy follows the same pattern: it increases to the right and upward, because smaller, more tightly held electron clouds require more energy to pull an electron away.
Atomic radius works in the opposite direction. Atoms get larger as you move left across a period and down within a group, because you’re adding more electron shells. Draw one arrow pointing left along the bottom and another pointing down along the right side. Label each arrow clearly with the property name and the word “increasing” so there’s no ambiguity about what the arrow represents.
Optional Labels for Extra Detail
Depending on the purpose of your table, you may want to include a few additional layers of information. Many reference tables indicate each element’s state of matter at standard temperature and pressure (about 25°C and normal atmospheric pressure) using text labels like “solid,” “liquid,” or “gas,” or by color-coding the element symbols. At room temperature, most elements are solid. Only bromine and mercury are liquid. Eleven elements are gases, mostly clustered in the upper right.
Some tables also include electron configurations inside each element box. These are written in shorthand notation, where the symbol of the nearest preceding noble gas goes in brackets, followed by the remaining electrons. Sodium, for example, is written as [Ne] 3s¹, meaning it has neon’s full configuration plus one additional electron in its 3s orbital. This notation is compact enough to fit in an element cell, but it’s typically only included on tables designed for upper-level chemistry work.
Whatever level of detail you choose, consistency matters most. Use the same format, font size, and placement for every element box so the table reads as a unified reference rather than a patchwork of labels.