Building a periodic table from scratch is one of the best ways to understand how chemistry is organized. Whether you’re making one for a class project, a wall poster, or a study tool, the process comes down to a grid of 7 rows and 18 columns, with each element placed by its atomic number and grouped by shared chemical behavior. Here’s how to construct one that’s both accurate and useful.
Start With the Grid: 7 Periods and 18 Groups
The modern periodic table arranges all 118 confirmed elements into 7 horizontal rows (called periods) and 18 vertical columns (called groups). Elements are placed left to right in order of increasing atomic number, which is simply the number of protons in an atom’s nucleus. Atomic number, not atomic weight, is what determines an element’s chemical identity and position. This was the key insight that transformed Mendeleev’s original 1869 table (organized by atomic mass) into the version we use today.
Draw or print a grid that’s 18 columns wide and 7 rows tall. The first row will only have two filled cells: one on the far left (hydrogen, element 1) and one on the far right (helium, element 2). The second and third rows each fill 8 cells, starting from the left. Rows 4 and 5 fill all 18 columns. Rows 6 and 7 also span all 18 columns, but each has a stretch of elements (14 per row) that gets pulled out and displayed separately at the bottom to keep the table from becoming unwieldy. These two separated rows are the lanthanides (elements 57–70) and actinides (elements 89–102).
What Goes Inside Each Element Cell
Every cell in your table represents one element and should contain a few key pieces of information. At minimum, include these four data points:
- Atomic number: the element’s position in the table, typically placed at the top of the cell. Hydrogen is 1, helium is 2, all the way up to oganesson at 118.
- Element symbol: the one- or two-letter abbreviation (H, He, Li, Be, etc.), displayed prominently in the center.
- Element name: the full name written below the symbol.
- Atomic mass: the weighted average mass of all naturally occurring isotopes, placed at the bottom. IUPAC publishes updated standard atomic weights periodically, with the most recent set released in 2023. For synthetic elements that don’t occur in nature, the mass number of the most stable known isotope is listed in brackets instead.
If you want a more detailed table, you can also include the element’s electron configuration, common oxidation states, electronegativity value, or state of matter at room temperature. For a first build, sticking to the four basics keeps things clean.
Color-Coding by Element Category
Color is what turns a wall of numbers into an intuitive reference. The most common approach is to color-code cells by element category. You have several systems to choose from, and you can layer more than one using background color, text color, or border color.
Metals, Nonmetals, and Metalloids
The broadest division splits elements into three types. Metals make up the vast majority of the table. They’re shiny, conduct heat and electricity well, and can be hammered into sheets or drawn into wires. They tend to lose electrons in chemical reactions. Nonmetals sit on the upper right side of the table. They’re generally poor conductors, often brittle as solids, and tend to gain or share electrons. A small group of metalloids (like silicon and germanium) straddle the boundary with properties of both. They sit along a staircase-shaped line running roughly from boron down to astatine. Metalloids are particularly notable as semiconductors, which is why silicon became the backbone of computer chips.
A simple three-color scheme (for example, blue for metals, yellow for nonmetals, green for metalloids) instantly communicates this division.
Chemical Families
For more detail, color each chemical family separately. The major families are:
- Alkali metals (Group 1, excluding hydrogen): soft, highly reactive metals that each have one electron in their outermost shell.
- Alkaline earth metals (Group 2): reactive metals with two outer electrons, including magnesium and calcium.
- Transition metals (Groups 3–12): the large central block, including iron, copper, gold, and silver.
- Halogens (Group 17): highly reactive nonmetals like fluorine, chlorine, and iodine that are one electron short of a full outer shell.
- Noble gases (Group 18): helium, neon, argon, and their neighbors, with completely filled outer electron shells, making them almost entirely unreactive.
- Lanthanides and actinides: the two rows displayed below the main table, where electrons fill a deeper inner shell.
Assigning a distinct color to each family makes the table much easier to read at a glance. Most published periodic tables use 9 or 10 colors to cover all the subcategories.
Understanding the Four Blocks
The table’s shape reflects how electrons fill energy levels, and this is worth understanding if you want your table to be more than decorative. The table divides into four rectangular blocks, each named after the type of electron orbital being filled:
- s-block: the first 2 columns on the left (Groups 1 and 2), plus hydrogen and helium. These elements are filling their outermost s orbital.
- d-block: the 10 columns in the middle (Groups 3–12), home to the transition metals.
- p-block: the last 6 columns on the right (Groups 13–18). As you move left to right across these columns, electrons fill the p orbital.
- f-block: the two separated rows at the bottom (lanthanides and actinides), where electrons fill the f orbital.
If you shade these four blocks lightly in the background, it adds a layer of information without cluttering the design. The block structure explains why the table has its distinctive shape: 2 columns on the left, a gap in the early rows, 10 columns in the middle, and 6 on the right.
Adding Trend Arrows
One of the periodic table’s most powerful features is that element properties change in predictable patterns across rows and down columns. Adding small arrows in the margins of your table can highlight these trends:
Atomic radius (the size of an atom) increases as you move down a column, because each new row adds another electron shell. It decreases as you move left to right across a row, because a stronger nuclear charge pulls electrons in tighter. Electronegativity, which measures how strongly an atom attracts electrons in a bond, follows the opposite pattern: it increases from left to right and decreases from top to bottom. Fluorine, in the upper right corner, is the most electronegative element. Ionization energy, the energy needed to strip away an electron, also increases from left to right and decreases from top to bottom.
A simple pair of arrows along the top and left margins, labeled with the trend name and direction, makes these patterns immediately visible.
Practical Tips for Building Your Table
If you’re making a physical poster, start by lightly penciling in the full grid before adding any data. The irregular shape of the first three rows is the trickiest part to get right. Row 1 has element 1 in column 1 and element 2 in column 18, with nothing in between. Rows 2 and 3 fill columns 1–2 and 13–18, leaving columns 3–12 empty. Starting at row 4, all 18 columns are filled.
For a digital version, spreadsheet software works surprisingly well. Set all columns to equal width, merge cells where needed for the gaps in the first three rows, and use cell fill colors for your categories. Each cell becomes a mini template you can populate with atomic number, symbol, name, and mass.
Use a consistent layout within each cell. The most common convention places the atomic number at top left, the symbol large and centered, the full name below it, and the atomic mass at the bottom. Keeping this identical across all 118 cells is what makes the finished table look professional.
For your atomic mass values, the IUPAC Commission on Isotopic Abundances and Atomic Weights maintains the definitive reference. Their 2023 standard atomic weights are freely available online and represent the most current accepted values. Using these ensures your table matches what’s published in textbooks and scientific journals.
The Gap at the Bottom
The two rows pulled out beneath the main table (lanthanides and actinides) technically belong in row 6, columns 3 through 16, and row 7, same columns. They’re separated purely for practical space reasons. If you inserted them into the main grid, your table would be 32 columns wide instead of 18, which is harder to print and read. Some “long form” periodic tables do display all 32 columns, and building one of those is a worthwhile exercise if you want to see the true unbroken structure. But for a standard table, pull them out, place them below, and use a small marker or line to show where they connect back to the main grid.
Your finished table should have 118 elements, ending with oganesson (element 118) in the bottom right corner of the main grid. All four elements in row 7’s p-block (nihonium, moscovium, tennessine, and oganesson) were officially named by IUPAC in November 2016, completing the seventh period. No elements beyond 118 have been confirmed yet.