How Many Groups and Periods Are in the Periodic Table? The Full Breakdown
Ever stared at the periodic table and felt a small wave of confusion? Even so, you're not alone. Plus, it's one of those things most of us half-remember from high school chemistry — and that's exactly why it's worth sorting out properly. Let's get into it.
What the Periodic Table Actually Is
The periodic table isn't just a chart your teacher hung on the wall. It's basically a master map of every known element, organized by the way their atoms behave. That last part matters more than most people realize.
Here's the thing — the table isn't arranged alphabetically, and it's not random either. Each element gets a spot based on how many protons it has (that's its atomic number*) and how its electrons are arranged. That electron arrangement is what determines if an element is going to behave like a shy introvert (think noble gases) or a hyperactive social butterfly (hello, alkali metals).
There are currently 118 confirmed elements on the table. In real terms, the most recent additions — nihonium, moscovium, tennessine, and oganesson — were officially recognized in 2016. Whether the table will keep growing depends on whether scientists can synthesize more elements in particle accelerators, which is a whole other rabbit hole.
How Many Groups Are in the Periodic Table?
There are 18 groups in the periodic table, and they run vertically — top to bottom. And each group is a column, and the elements inside one column share similar chemical behavior. Also, that's the magic of it. Place sodium in group 1, and you can bet it'll act a lot like the other alkali metals sitting above and below it.
The groups even have names in some cases. So group 2? And group 17? Even so, those are the alkali metals*. Practically speaking, group 18? In practice, the alkaline earth metals*. Halogens*. Think about it: group 1? Noble gases* — the non-reactors of the chemistry world.
One quirky exception: the two rows that sit at the bottom of most printed tables. The lanthanides and actinides technically belong in groups 3 through... Consider this: well, they got separated for space reasons. They're usually displayed below the main table to keep things tidy, but they still count as part of the 18-group structure.
So if someone asks you, "how many groups are in the periodic table?Still, " — 18. Every time.
How Many Periods Are in the Periodic Table?
Now flip your perspective. The horizontal rows are called periods, and there are 7 of them.
Each period represents a new energy level being added to an atom. And so on. Period 3 has eight. Period 4 has 18. Period 1 has just two elements (hydrogen and helium) because the first electron shell only holds two electrons. Period 2 has eight. The pattern isn't random — it follows the rules of quantum mechanics, but you don't need to dive that deep to use the table.
What you should know is that as you move left to right across a period, elements change from metals to nonmetals. That shift is one of the most useful patterns in all of chemistry.
Why the Group and Period Setup Actually Matters
Here's where it gets practical. The whole point of organizing the table this way is so you can predict* things. You don't have to memorize every single property of every element. Just look at where it sits.
Want to know if an element will react violently with water? But look at group 1. Want to know if it'll barely react with anything at all? Which means group 18 is your friend. In practice, need to estimate an element's atomic radius or electronegativity? Trends run predictably across periods and down groups.
This is the part most people sleep on. Because of that, the periodic table isn't a list. It's a tool. And once you understand the logic behind the rows and columns, it stops feeling like a wall of random letters and starts feeling like a cheat sheet.
Common Mistakes People Make With the Periodic Table
Mixing Up Groups and Periods
This is, by far, the most common slip. But it sounds simple until you're halfway through a quiz and suddenly second-guessing yourself. Groups are vertical. Here's the thing — periods are horizontal. A quick memory trick: groups go up and down like a tall building, and periods go side to side like a long sentence.
Forgetting About the Lanthanides and Actinides
That floating block at the bottom? Those aren't extra elements that snuck in. They're part of the table, just displayed separately to keep the main grid from becoming a wide, unreadable mess. The lanthanides fit into period 6, and the actinides fit into period 7. Knowing this matters when you're trying to count periods correctly.
For more on this topic, read our article on protons and neutrons are found in the or check out what are the three parts of the atom.
Assuming Every Group Is the Same Length
Nope. Some groups are short. Some are long. Group 8 is a transition metal group with a different lineup. Still, group 1 has lithium, sodium, potassium, rubidium, cesium, and francium. The shape of each column tells you something about electron shells and orbital filling.
Thinking the Table Is "Finished"
The periodic table is a working document. It started with around 60 elements in the 1800s and has grown steadily. In real terms, new elements are synthetically created in labs, and yes, the table will probably expand again. Each new addition gets a temporary placeholder name based on its atomic number (like ununoctium before oganesson got its official title).
Tips for Actually Learning This Stuff
Don't Just Memorize — Look for Patterns
The first time you look at the periodic table, focus on color and shape, not individual elements. Notice the metals clustered on the left. Also, see the nonmetals on the right. Spot the staircase line that separates them. These visual cues stick way better than raw numbers.
Build a Mental Anchor
Pick three or four elements you already know well — gold, oxygen, carbon, maybe sodium — and find them on the table. Then use those as reference points. "What's near oxygen?" is a much easier question to answer than "Where's selenium again?
Learn the Trends, Not Just the Facts
Things like electronegativity*, atomic radius*, and ionization energy* all follow predictable paths across periods and down groups. Once you learn the trends, you can answer questions about elements you've never even heard of.
Use a Simple Mnemonic for Group Numbers
If you ever need to recall which groups are which, try this for group 1: "LiNa K Rb Cs Fr" — pronounced "linakerbcsfr." Weird? Yes. Effective? Surprisingly, also yes.
FAQ
Are there exactly 18 groups in the periodic table?
Yes. Here's the thing — the IUPAC officially recognizes 18 groups, numbered 1 through 18 from left to right. Older textbooks may use a different numbering system (IA through VIIIA), but the count is the same.
How many periods are in the periodic table right now?
Seven. Period 7 is the current bottom row and includes the actinides and the recently named elements up to oganesson (element 118).
Why are some elements shown below the main table?
The lanthanides and actinides are pulled out for layout reasons. On top of that, if they were placed in their natural positions, the table would be awkwardly wide and harder to read. They're still part of periods 6 and 7, just visually separated.
Could there be a period 8 someday?
In theory, yes — but it would require synthesizing elements with atomic numbers 119 and above. Scientists have been chasing this for years, and a few labs believe they're close. Don't expect it in your average chemistry class just yet, though.
Is the periodic table arranged by atomic number or atomic mass?
Atomic number. Earlier tables were organized by atomic mass, but once scientists understood atomic structure, atomic number proved to be the better organizing principle because it lines up more cleanly with chemical behavior.
Wrapping It Up
So — 18 groups, 7 periods, 118 elements (for now). In practice, the periodic table isn't there to be memorized. Worth adding: once you understand the logic behind the columns and rows, the whole thing starts to click. And honestly, that's the real lesson. The table might look intimidating at first glance, but it's really just a clever system for organizing the building blocks of everything around you. It's there to be used*.
