What Is the Periodic Table?

Everything Is Made of Elements

Look around you. Your phone, the air, your own body — everything is made of elements, pure substances that can't be broken down into anything simpler by chemical means. Hydrogen, oxygen, carbon, iron, gold — these are all elements. Scientists have discovered 118 elements so far, and the periodic table is the chart that organizes all of them in a way that reveals patterns and relationships.

How It's Organized

Elements are arranged by atomic number — the number of protons in an atom's nucleus. Hydrogen has 1 proton (atomic number 1), helium has 2, lithium has 3, and so on up to oganesson with 118. The table is arranged in rows called periods (7 periods) and columns called groups (18 groups). Elements in the same group share similar chemical properties — they behave in similar ways.

Metals, Nonmetals, and Metalloids

Most elements are metals — shiny, good conductors of heat and electricity, and usually solid at room temperature. They occupy the left and center of the table. Nonmetals sit on the upper right — they're often gases or brittle solids, poor conductors, and include essentials like oxygen, nitrogen, and carbon. In between sit metalloids (like silicon), which have properties of both.

Famous Groups

Group 1 (alkali metals) like sodium and potassium are so reactive they explode on contact with water. Group 17 (halogens) like chlorine and fluorine are highly reactive nonmetals. Group 18 (noble gases) like helium, neon, and argon are the opposite — they almost never react with anything because their electron shells are already full. The noble gases' stability is the key to understanding why atoms bond: most atoms are trying to achieve a noble-gas-like electron configuration.

Why It's Called "Periodic"

The word "periodic" means "repeating at regular intervals." Russian chemist Dmitri Mendeleev noticed in 1869 that when elements are arranged by atomic weight, their properties repeat in a regular pattern — metals, then metalloids, then nonmetals, then noble gases, over and over. He even left gaps in his table for elements that hadn't been discovered yet and predicted their properties. When those elements were found years later, his predictions were astonishingly accurate.

Why This Matters

The periodic table is the master map of all matter in the universe. Every object you can touch, taste, or smell is made from the elements organized in this table. When children learn the periodic table, they're learning the alphabet of chemistry — and just as knowing letters leads to reading words and sentences, knowing elements leads to understanding compounds, reactions, and the materials that make up everything around us.

The periodic table is also a triumph of scientific pattern recognition. Dmitri Mendeleev arranged elements by atomic weight and noticed repeating patterns in their properties — and his table was so well-organized that he could predict the properties of elements that hadn't even been discovered yet. Learning this story teaches children that science is about finding order in apparent chaos.

Where Kids Get Stuck

The most overwhelming aspect for children is the sheer size — 118 elements feels impossible to learn. The key is to start small: focus on the first 20 elements (hydrogen through calcium), which account for the vast majority of matter children encounter in daily life. Water (hydrogen + oxygen), table salt (sodium + chlorine), and carbon in living things are all within this manageable subset.

Another confusion is the difference between an element and a compound. Children may think water (H₂O) is an element because it's a common substance. Understanding that elements are pure substances that can't be broken down further, while compounds are combinations of elements, is the crucial conceptual leap.

Students also struggle with why the table is arranged the way it is. Rows (periods) represent energy levels, and columns (groups) represent elements with similar chemical properties. Without understanding atomic structure, this organization seems arbitrary. Using group 18 (noble gases: they all resist reacting) as a concrete example of "elements in the same column behave alike" makes the logic visible.

Try This at Home

• Element scavenger hunt — Find items around your house and identify their primary elements: iron nails (Fe), aluminum cans (Al), copper pennies (Cu), helium balloons (He).
• Element flash cards — Make cards for the first 20 elements with symbol, name, and one fun fact. Quiz each other using symbols only.
• Periodic table coloring — Print a blank periodic table and color-code it by type: metals, nonmetals, metalloids, noble gases. Look for patterns in where each group appears.
• Element song or poem — Create a rhyme or tune to remember the first 10 or 20 elements in order. Musical memory is powerful!

For more ideas, see our guide: Teaching Kids the Periodic Table.

Last reviewed: May 2026