Periodic table facts for kids

The periodic table of chemical elements is a special chart that lists all the known chemical elements. Think of it like an organized list of all the basic building blocks of everything around us! As of 2022, scientists have found and confirmed 118 different elements.

In this amazing table, elements are placed in order based on their atomic number. This number starts with 1 for hydrogen, which is the lightest element. An element's atomic number tells you how many protons are in the center (nucleus) of one of its atoms.

The periodic table is arranged into rows called periods and columns called groups.

• A row across the table is a period. Periods are numbered from 1 to 8.
• Period 1 has only two elements: hydrogen and helium.
• Periods 2 and 3 each have 8 elements. Other periods are longer.
• Elements in the same period have atomic numbers that go up one by one.

A column down the table is called a group. There are 18 groups in the standard periodic table, numbered from 1 to 18. Elements in the same group often have similar ways their electrons are arranged. This means they usually behave in similar chemical ways. For example, group 18 elements are called noble gases. They are all gases and usually don't mix with other atoms.

The standard version of the periodic table, showing all the elements.

For a long time, groups were numbered using Roman numerals (like I, II, III). But in 1990, a group of scientists called the International Union of Pure and Applied Chemistry (IUPAC) decided to use the simpler Arabic numerals (1, 2, 3) for group numbers.

Scientists called chemists use the periodic table to find patterns and connections between elements. There are three main types of elements in the table: metals, metalloids (which are like a mix), and nonmetals. For example, elements at the bottom and far left of the table are the most metallic. Elements at the top right are the least metallic. This means cesium is much more metallic than helium. Many other cool patterns exist too!

The periodic table was created by a Russian chemist named Dmitry Ivanovich Mendeleyev (1834-1907). To honor him, element 101 was named mendelevium.

What the Periodic Table Looks Like

The most common way to show the periodic table is below. It helps us see how elements are organized.

Understanding the Colors and Borders

The colors and borders around each element box in the table tell us more about them!

Chemical Series of the Periodic Table

• Alkali metals
• Alkaline earths
• Lanthanides
• Actinides
• Superactinides
• Transition metals
• Poor metals
• Metalloids/Semi metals/Half metals
• Nonmetals
• Halogens
• Noble gases

State at normal conditions

The color of the number (the atomic number) above the element symbol shows what state the element is in at normal room temperature and pressure:

• Blue numbers mean the element is a gas.
• Green numbers mean the element is a liquid.
• Black numbers mean the element is a solid.

Radioactivity

The type of border around an element's box tells us about its stability:

• Elements with solid borders have stable forms (called primordial elements).
• Elements with dashed borders only have naturally occurring forms that are radioactive.
• Elements with dotted borders do not occur naturally; they are made by scientists (Synthetic Elements).
• Elements without borders are too radioactive to have been found yet.

The History of the Periodic Table

Dmitri Mendeleev's periodic table from 1871. He left question marks for elements he predicted would be discovered.

The idea of organizing the elements is not new. As early as 1817, a scientist named Johann Wolfgang Döbereiner noticed that he could group some elements into threes, which he called triads. The elements in each triad had similar properties.

The big breakthrough came in 1869 from a Russian chemist named Dmitri Mendeleev. He wrote down the properties of each known element on a card and began arranging them. He noticed that if he put them in order of their atomic weight, a pattern appeared.

Mendeleev's genius was that he wasn't afraid to leave gaps in his table. He predicted that these gaps were for elements that had not yet been discovered. He even described the properties of three of these missing elements. Within 15 years, all three elements—gallium, scandium, and germanium—were discovered, and their properties matched Mendeleev's predictions almost perfectly. This made the scientific world realize how powerful his table was.

Later, scientists like Henry Moseley discovered that it was the atomic number (the number of protons), not the atomic weight, that was the key to the order of the elements. This discovery cleared up a few problems in Mendeleev's table and led to the modern periodic table we use today.

The Future of the Periodic Table

The seventh row of the periodic table was completed in 2016 with the naming of four new elements: nihonium (113), moscovium (115), tennessine (117), and oganesson (118). So what's next?

Scientists are now trying to create elements for an eighth row, starting with element 119. These are called superheavy elements. Creating them is incredibly difficult. Scientists have to smash smaller atoms together in powerful machines called particle accelerators, hoping they will stick together for a fraction of a second.

Researchers are also searching for an "island of stability". This is a theory that suggests there might be certain superheavy elements that are much more stable than the ones created so far. If such elements could be made, they might have amazing new properties that we can't even imagine yet. The quest to expand the periodic table is an exciting frontier of science.

Other Ways to See the Elements

While the table above is the most common, scientists have thought of other cool ways to show the periodic table:

• 

  This spiral arrangement by Theodor Benfey places elements around hydrogen. Their atomic weight helps decide their spot.

• 

  Dmitry Ivanovich Mendeleyev also tried a flower-like design. The Actinides and Lanthanides are shown as loops next to the main part.

• 

  Timothy Stowe organized elements based on their quantum numbers.

• 

  Betterman arranged elements by their isoelectric properties.

• 

  A triangular version of the periodic table by Zmaczynski and Bayley.

• 

  This version arranges the elements in a pyramid shape.

More Ways to Explore Elements

There are many different versions and lists of elements you can find:

• A vertical table can be easier to read on computer screens.
• The big table shows the basics plus the full names of elements.
• The huge table includes full names and atomic masses.
• You can also find tables showing Electron configurations.
• There are tables that highlight metals and non-metals.
• A list of elements includes their name, symbol, atomic number, atomic mass, group, and period. You can sort this list by any of these details!
• You can also find a list of elements by symbol.
• Or lists of elements by their boiling point, melting point, or density.

Related Pages

• Periodic table group
• Periodic table period
• Extended periodic table

Images for kids

• 

  3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)

• 

  Idealized order of shell-filling (most accurate for   n  ≲ 4 .)

• 

  Trend in atomic radii

• 

  Flowing liquid mercury. Its liquid state at room temperature is a result of special relativity.

• 

  Mendeleev's 1869 periodic table

• 

  Mendeleev's 1871 periodic table

• 

  Dmitri Mendeleev

• 

  Henry Moseley

• 

  Glenn T. Seaborg

• 

  Iron, a metal

• 

  Sulfur, a nonmetal

• 

  Arsenic, an element often called a semi-metal or metalloid

See also

In Spanish: Tabla periódica de los elementos para niños